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Professor YAO Wang Receives Huang Kun Prize for Solid Physics and Semiconductor Physics

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HKU Science Takes the Lead in Environmental Research Funding, Securing Over Eight Million Dollars for Seven Innovative Projects

Our primary focus at the HKU Faculty of Science is to champion sustainable development and environmental conservation. We are proud to announce that HKU topped the Environmental Research, Technology Demonstration and Conference Projects 2022/23 funding, with 10 projects receiving a total of $9,882,800. Among these, 7 projects are from the Faculty of Science, marking the highest number in the past years and securing a total amount of $8,407,976.  Our researchers are dedicated to developing innovative technologies and practices that enhance the environment and preserve valuable resources.  The funded projects encompass a diverse range of topics, spanning from marine biodiversity to sustainable energy solutions. These projects aim to provide practical and effective solutions to pressing environmental issues. Moreover, their outcomes hold the potential for general adoption within the local environmental fields in Hong Kong. Awarded Project Summary No. Project Coordinator Department/School Project Title Approved Budget (HKD) Duration (No. of Months) 1 Professor Gray A. WILLIAMS School of Biological Sciences;  Swire Institute of Marine Science Environment and Conservation Fund - Connecting the dots: a standardized and quality-assured marine biodiversity database for Hong Kong $1,021,000 24 2 Dr Mathew SEYMOUR School of Biological Sciences Environment and Conservation Fund - Hong Kong Chironomidae biodiversity: an initial assessment of the largest freshwater insect group and their link with ecologically important stream conservation $1,300,000 24 3 Dr Juan Diego GAITÁN-ESPITIA School of Biological Sciences;  Swire Institute of Marine Science Environment and Conservation Fund - Assessing and monitoring ecological dynamics of seagrass ecosystems in Hong Kong: Tools for management and restoration efforts   $2,307,296 36 4 Professor David L. PHILLIPS Department of Chemistry Environment and Conservation Fund - Towards Livable & Healthy City: Solar-Driven Exhaust Fume (NOx) Purification Engineering for Eco-Friendly Transportation and Electricity Generation in Hong Kong $1,083,000 36 5 Dr Celia M. SCHUNTER School of Biological Sciences Environment and Conservation Fund - Fish Community Monitoring: Environmental Factors and Marine Protected Area Effectiveness $1,306,000 30 6 Dr Stephen C.Y. NG Department of Physics Environment and Conservation Fund - Exploratory Study of the Impact of Artificial Light at Night on Birds at Mai Po Nature Reserve $499,880 24 7 Dr David M. BAKER School of Biological Sciences;  Swire Institute of Marine Science Environment and Conservation Fund - A mammoth task: creating a reliable and cheap test to distinguish mammoth and elephant ivories to prevent trafficking and laundering of elephant ivory $890,800 24  

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Elevating Imaging Quality to a New Height: HKU Physicists Employ Synthetic Complex Frequency Waves to Overcome Optical Loss in Superlenses

A collaborative research team led by Interim Head of Physics Professor Shuang ZHANG from The University of Hong Kong (HKU), along with National Center for Nanoscience and Technology, Imperial College London and University of California, Berkeley, has proposed a new synthetic complex frequency wave (CFW) approach to address optical loss in superimaging demonstration. The research findings were recently published in the prestigious academic journal Science. Imaging plays an important role in many fields, including biology, medicine and material science. Optical microscopes use light to obtain imaging of miniscule objects. However, conventional microscopes can only resolve feature sizes in the order of the optical wavelength at best, known as the diffraction limit. To overcome the diffraction limit, Sir John Pendry from Imperial College London introduced the concept of superlenses, which can be constructed from negative index media or noble metals like silver. Subsequently, Professor Xiang ZHANG, the current President and Vice-Chancellor of HKU, along with his then team at the University of California, Berkeley, experimentally demonstrated superimaging using both a silver thin film and a silver/dielectric multilayer stack. These works have extensively promoted the development and application of superlens technology. Unfortunately, all superlenses suffer from inevitable optical loss, which converts optical energy into heat. This significantly affects the performance of optical devices, such as superimaging lenses, which rely on the faithful delivery of information carried by light waves. Optical loss has been the main limiting factor that has constrained the development of nanophotonics for the past three decades. Many applications, including sensing, superimaging, and nanophotonic circuits, would greatly benefit if this problem could be solved. Professor Shuang Zhang, corresponding author of the paper and also Interim Head of HKU Department of Physics, explained the research foci, ‘To solve the optical loss problem in some important applications, we have proposed a practical solution — using a novel synthetic complex wave excitation to obtain virtual gain, and then offset the intrinsic loss of the optical system. As a verification, we applied this approach to the superlens imaging mechanism and theoretically improved imaging resolution significantly.’ ‘We further demonstrated our theory by conducting experiments using hyperlenses made of hyperbolic metamaterials in the microwave frequency range and polariton metamaterials in the optical frequency range. As expected, we obtained excellent imaging results consistent with our theoretical predictions,’ added Dr Fuxin GUAN, the paper’s first author and a Postdoctoral Fellow at HKU. Multi-frequency approach to overcome optical loss In this study, the researchers introduced a novel multiple-frequency approach to overcome negative impacts of loss on superimaging. Complex frequency waves can be used to provide virtual gain to compensate for the loss in an optical system. What does complex frequency mean? Frequency of a wave refers to how fast it oscillates in time, as shown in Figure 2a. It is natural to consider frequency a real number. Interestingly, the concept of frequency can be extended into the complex domain, where the imaginary part of the frequency also has a well-defined physical meaning, i.e., how fast a wave amplifies or decays in time. Hence, for a complex frequency wave, both oscillation and amplification of the wave occurs simultaneously. For a complex frequency with negative (positive) imaginary part, the wave decays (amplifies) in time, as shown in Figure 2b. Of course, an ideal complex wave is not physical because it would diverge when time goes to either positive or negative infinity, depending on the sign of its imaginary part. Hence, any realistic implementation of complex frequency waves needs to be truncated in time to avoid the divergence (see Figure 2c). The optical measurement directly based on complex frequency waves needs to be performed in the time domain and it would involve complicated time-gated measurements and therefore it has not been experimentally realised thus far.   Figure 2. Electric field profile of waves in real frequency (a), complex frequency (b), and truncated complex frequency (c). Truncated complex frequency wave synthesised by the linear combination of multiple real frequencies (d). Image credit: HKU   The team utilised mathematical tool Fourier Transformation to break down a truncated CFW into many components of different real frequencies (see Figure 2d), greatly facilitating the implementation of CFWs for various applications, such as superimaging. By carrying out optical measurements at multiple real frequencies at a fixed interval, it is possible to construct the optical response of the system at a complex frequency by mathematically combining that of real frequencies. As a proof of concept, the team started with superimaging at microwave frequencies using a hyperbolic metamaterial. The hyperbolic metamaterial can carry waves with very large wavevectors (or equivalently very small wavelengths), that are capable of transmitting the information of very small feature sizes. However, the larger the wavevector, the more sensitive the waves are to optical loss. Therefore, in the presence of loss, the information of those small feature sizes gets lost during the propagation inside the hyperbolic metamaterial. The researchers showed that, by appropriately combining the blurred images measured at different real frequencies, a clear image at a complex frequency was formed with a deep-subwavelength resolution in Figure 3.   Figure 3. Imaging patterns in multiple real frequencies and complex frequency of the letter ‘H’. Image credit: HKU The team further extended the principle to optical frequencies, employing an optical superlens made of a phononic crystal called silicon carbide, which operates at the far-infrared wavelength of around 10 micrometers. In a phononic crystal, the lattice vibration can couple with light to create the superimaging effect. However, the loss is still a limiting factor in the spatial resolution. Although the spatial resolutions of imaging at all the real frequencies were limited by the loss, as shown by the blurred images of the nano-scale holes, ultrahigh-resolution imaging can be obtained with synthesised CFWs that consist of multiple frequency components (see Figure 4). Figure 4. Super-imaging using a SiC superlens operating at optical frequency. Complex frequency measurement provide a much better spatial resolution than that of a real frequency. SEM image shows the object performance. Image credit: HKU ‘The work has provided a solution to overcome optical loss in optical systems, a long-standing problem in nanophotonics. The synthesised complex-frequency method can be readily extended to other applications, including molecular sensing and nanophotonic integrated circuits,’ said Professor Xiang ZHANG, another corresponding author of the paper, the President and Vice-Chancellor of HKU, and also Chair of Physics and Engineering. He hailed this as a remarkable and universally applicable method, ‘This can be leveraged to tackle loss in other wave systems, including sound waves, elastic waves, and quantum waves, elevating imaging quality to a new height.’ This work was supported by the New Cornerstone Science Foundation, the Research Grants Council of Hong Kong. Journal paper: ‘Overcoming losses in superlenses with synthetic waves of complex frequency’, Science. The journal can be accessed here: https://www.science.org/doi/10.1126/science.adi1267 More information about Professor Shuang Zhang: https://shorturl.at/efCN1  

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Geologists Team at HKU Becomes First in Hong Kong to Retrieve Lunar Samples Set to Unveil the Mysteries of the Moon's Volcanic History

The geologists at The University of Hong Kong (HKU) have achieved a historic feat by obtaining lunar soil samples collected by the Chinese lunar probe Chang'e-5 in 2020. This marks the first time that a Hong Kong research team has secured such samples. Led by postdoctoral fellow Dr Yuqi QIAN from the Department of Earth Sciences, Faculty of Science, the team obtained approval from the China National Space Administration's Lunar Exploration and Space Engineering Centre to study the lunar soil samples. Dr Qian personally travelled to Beijing to retrieve the samples, which weigh 822.6 milligrams in total. These lunar samples offer valuable insights into the Moon’s geological and thermal history and its connection to the formation and evolution of planetary bodies in the Solar System. The achievement by the HKU team underscores the university's growing contributions to China's lunar and planetary exploration efforts.   ‘This is a dream come true for us and Hong Kong's space science community,’ said Qian, who is eager to analyse the samples using state-of-the-art instruments at the university. ‘We hope to reveal the secrets of the Moon and gain insights into the early Earth, which could have important implications for our understanding of the Solar System and beyond.’ Previous Study on the Chang'e-5 Landing Site Paves the Way Dr Qian is making waves in the field of planetary geology with his exceptional research on the Chang'e-5 landing site. Having published the first paper documenting the site and constructing a complete picture, he has been focusing on different aspects such as regolith properties, volcanic history and the provenance of lunar soils. His research work has been published in top-tier journals and widely cited, with over 400 citations, solidifying his position as an emerging expert. Recently, Dr Qian joined HKU as a postdoctoral fellow after obtaining his doctoral degree in Planetary Geology from China University of Geosciences. Drawing on years of research on the Moon, the most exhilarating moment of his research career was an exciting discovery regarding the latest volcanic activity on the Moon’s surface – he discovered that the eastern part of the pre-selected Chang'e-5 landing region contained one of the youngest mare basalts on the Moon. Recognising the scientific significance of this finding, he proposed that Chang'e-5 should explore this region to collect these young basalts, which were younger than any previously returned lunar basalts. In 2020, Chang'e-5 successfully landed on the lunar surface within the Procellarum KREEP Terrane, a chemical anomaly province known for its elevated heat-producing elements and lunar volcanic deposits. Upon analysing the samples collected from this region, scientists were stunned to discover that the basalts were 2.0 billion years old - almost 1 billion years younger than any previous lunar volcanic samples collected by Apollo or Luna missions. This ground-breaking discovery confirmed Dr Qian's prediction and has reshaped our understanding of lunar history. It has also raised the question: how did the young volcanism originate?   Dr Qian had been working tirelessly on this question, using remote sensing techniques to explore the volcanic history of the Chang'e-5 landing site. His previous research proposed that the Chang'e-5 basalts originated from the source vent of Rima Sharp, whose channel is only ~15 km from the landing site. Rima Sharp is a lunar sinuous rille whose formation required tons of lavas and was highly likely to be sampled by Chang'e-5. Gearing up for Insights into Moon's Volcanic History and Evolution of Planetary Bodies in the Solar System After joining HKU, Dr Qian recognised the potential of the support and resources available at the university to make progress in understanding young lunar volcanism with samples. When Dr Qian learned about the sixth batch of lunar research samples is open for application earlier this year, he swiftly mobilised scientists in the department to join his application. ‘I knew this was an opportunity we could not miss for the further development of lunar science at HKU and with our collaborators throughout Hong Kong,’ said Dr Qian. With the support of Dr Joseph MICHALSKI of the Department of Earth Sciences, an expert with extensive experience in planetary geology and mineralogy, Dr Qian formed a team to apply for the lunar samples. Other members of the department included Professor Guochun ZHAO, a renowned geologist specialising in tectonic processes and the evolution of the Earth's lithosphere; Dr Weiran LI, a volcanologist specialising in magmatism, volatile cycling, and volcanic hazards; Professor Min SUN, a prominent geochemist focusing in the evolution of old continents; Professor Jian ZHANG, a structural geologist with expertise in crustal growth and tectonic evolution; and Dr Yiliang LI, an astrobiologist whose research centres in the search for life beyond Earth.  As the Deputy Director and member of the Laboratory for Space Research (LSR) respectively, Dr Michalski and Dr Qian fulfill one of the laboratory's research foci centres around Lunary and Planetary Sciences.   Now, armed with the returning samples and his previous research, Dr Qian and the team can link remote sensing and laboratory studies to unravel the secrets behind the lunar basalts and address the question that has puzzled scientists about the origins of young volcanism on the Moon. The team aims to use petrological-volcanological and spectroscopic techniques to reconstruct and study lunar magmas’ generation, ascent, and eruption, focusing on the evolution of volatiles in the lunar soil samples. By analysing the volatiles in the samples, the team hopes to gain insights into the history of lunar late volcanism and the distribution and evolution of volatiles in the Moon's magma system, providing valuable information about the Moon's geological and thermal history and its connection to the formation and evolution of the Solar System in the future. Dr Qian’s supervisor Dr Joseph Michalski established the Planetary Spectroscopy and Mineralogy Lab at HKU, with the aim of providing laboratory support for space missions. He stated that the successful acquisition of lunar samples from the Chang'e-5 mission proved the value of the laboratory and expressed his hope for future collaborations in sample research. He said, ‘We are also proud to work with our collaborators at the Hong Kong Polytechnic University and other universities in HK to build a strong space research community, that might help with our future collaborations and explorations.’ Dr Qian expressed that he is thrilled to be part of the effort to explore the Moon, Mars, and beyond. He stated, ‘I believe that space exploration is crucial for humanity's future. It is an exciting time to be involved in this field, and I hope our research will inspire future generations to continue exploring and expanding our knowledge of the vast space.’ In addition to studying the samples collected by Chang'e-5, Dr Qian eagerly anticipates the upcoming Chang'e-6 mission to the lunar farside. He hopes to conduct further research on lunar geology based on China’s future lunar missions, especially the crewed ones and the International Lunar Research Station, which could provide valuable insights into the formation and evolution of the Moon and lead human’s way to other worlds. More information about Dr Yuqi Qian: https://yuqiqian.com More information about Dr Joseph Michalski: https://www.clays.space   

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HKU Earth Science scholar Dr Joseph Michalski Becomes the first non-Chinese recipient of Xplorer Prize

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Three HKU Science Academics Recognised for Research Excellence and Innovation in RGC Funding Schemes

Three academics from our Faculty have been recognised for their research excellence and innovation in the latest funding exercises by the Research Grants Council (RGC). Professor Shuang ZHANG, Chair of Physics in the Department of Physics, is the leader of the ‘Photonic Integrated Platforms Based on Topological Physics’ project, which secured HK$10M under the Strategic Topics Grant. The project aims to create dynamic and programmable photonic circuits with advanced functionalities by combining recent advances in topological and integrated photonics.  In addition to Professor Zhang's achievement, Professor Xuechen LI in the Department of Chemistry was awarded Senior Research Fellow(SRFS), and Dr Joseph MICHALSKI in the Department of Earth Sciences was awarded Research Fellow(RFS).  The RGC funding schemes support research across a range of disciplines and are highly competitive. The recognition of these three academics is a testament to their exceptional research and the innovative projects they are leading. More details on HKU's funding results can be found at https://www.rss.hku.hk/funding/funding-results

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New Enzyme Discovered by HKU Plant Biochemists Unlocks Potential for Health-Promoting Compounds in Sorghum

Stilbenes are natural compounds found in various plants that have shown potential health benefits for humans, with a unique chemical structure consisting of two aromatic rings linked by a double bond. While resveratrol, found in grapes and red wine, is the most well-known stilbene, there has been increasing interest in other types of stilbenes that could offer additional health benefits. O-methylated stilbenes, which are produced by introduction of a methyl group (-CH3) to a hydroxyl (-OH) group on the stilbene backbone, are promising compounds for research. Some plant species, such as sorghum and wild sugarcane, have been found to produce different types of O-methylated stilbenes in response to abiotic or biotic stress and may have greater potency and bioavailability than non-methylated stilbenes. This makes these plant species particularly interesting for research on the biosynthesis of O-methylated stilbenes and potential applications in developing functional foods, nutraceuticals, and pharmaceuticals. Biosynthesis of O-methylated stilbenes. In sorghum, SOMT converts resveratrol to pinostilbene and pterostilbene which are O-methylated in the stilbene A-ring.  In wild sugarcane, a COMT likely converts piceatannol to isorhapontigenin which is O-methylated in the stilbene B-ring. O-methylation is a common modification that increases potency and bioavailability of phytochemicals. O-methylated groups are indicated in pink.   Recently, a research team led by Dr Clive LO from the School of Biological Sciences at The University of Hong Kong (HKU) collaborated with laboratories at the University of Queensland (UQ), Australia, and the HKU School of Biomedical Sciences (SBMS), as well as scientists in Mainland China and Japan, to discover a novel stilbene O-methylase (SbSOMT) in sorghum, an enzyme which is responsible for catalyzing the production of O-methylated stilbenes. The discovery offers a new avenue for producing O-methylated stilbenes in larger quantities and at lower costs, which could lead to the development of new functional foods, nutraceuticals, and pharmaceuticals that harness the potential health benefits of these compounds. The research findings have recently been published in Nature Communications.  Background Stilbenes are natural compounds found in plants with promising nutraceutical properties, known to provide a range of health benefits such as anti-ageing, anti-neurodegeneration, anti-diabetes, and chemo-preventive properties. O-methylation is a chemical process that can significantly enhance the potency and bioavailability of stilbenes. However, the biosynthesis of O-methylated stilbenes has not been well-studied, and further research is needed to generate specific stilbene compounds. The research team conducted a study that showed how sorghum and wild sugarcane could produce different types of O-methylated stilbenes, such as pinostilbene, pterostilbene and isorhapontigenin. They used advanced genetic techniques, including CRISPR-Cas9 mutagenesis and sorghum transformation, to identify the key enzyme, SbSOMT, that mediates the specific chemical modification of stilbene called 3,5-bis-O-methylation in sorghum. This modification affects the biological activity of the stilbene, including its antioxidant and anti-inflammatory properties. The team also conducted phylogenetic analysis to study the evolutionary relationships between different organisms, and found that SbSOMT is unique to Sorghum plants and originated from a group of related proteins called caffeic acid O-methyltransferases (COMTs) commonly found in all other grasses. In addition, the team presented the first crystal structure for SbSOMT in collaboration with HKU SBMS protein structural biologists.Research Significance The researchers discovered that SbSOMT uses a chemical reaction similar to COMTs in the grass family, but it binds to the stilbene molecule differently. This different binding mode allows SbSOMT to modify the stilbene molecule in a specific way that produces different types of O-methylated stilbenes in sorghum. These different types of stilbenes are characterized by the location of the O-methyl group on the stilbene molecule, either on the A-ring or the B-ring. In sorghum, SbSOMT modifies stilbenes in a way that produces A-ring O-methylated stilbenes, such as pinostilbene and pterostilbene. Meanwhile, wild sugarcane uses a common COMT enzyme to modify stilbenes to produce B-ring O-methylated stilbenes, such as isorhapontigenin. The difference between the A-ring and B-ring O-methylated stilbenes is due to the specific way that SbSOMT interacts with the stilbene molecule, which involves the hydrophobic Ile144 and Phe337 residues in the SbSOMT enzyme. The research has found that sorghum and wild sugarcane can potentially be used to produce O-methylated stilbenes. These compounds have health benefits and can be used in nutraceuticals (which are like dietary supplements). The team also discovered the enzymes responsible for producing these compounds in these plants.  Their findings suggest that we could use molecular breeding and transgenic approaches to create specific types of O-methylated stilbenes with even more health benefits. This could open up new possibilities for creating healthier food and supplement options.   Structural analysis of sorghum stilbene O-methylase (SbSOMT). A. SbSOMT (pink) shows high global structural similarity to SbCOMT (blue). SbSOMT is a unique OMT in Sorghum spp. while COMT is a common and widespread OMT enzyme. B. Close-up view of the substrate binding pocket docked with piceatannol. In SbSOMT (pink) and SbCOMT (blue), the stilbene A-ring and B-ring are positioned close to a key catalytic residue (H267/H282), respectively, for O-methylation. Images adapted from Nature Communications, 2023, doi:10.1038/s41467-023-38908-5 This research was supported by the Hong Kong Research Grants Council. The HKU Libraries Open Access Author Fund provided support for the publication. The journal paper, entitled “Regioselective stilbene O-methylations in Saccharinae grasses. Nat. Commun 14, 3462 (2023)”, can be found at the following link: https://doi.org/10.1038/s41467-023-38908-5     

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HKU and Manchester University Astronomers come closer to finding answers about mysterious alignment of ghost stars

Scientists who discovered evidence of an unusual and mysterious alignment of planetary nebulae in the central bulge of our galaxy ten years ago, have now obtained a much stronger result and have also now discovered what might cause it. Astronomers from The University of Hong Kong and the University of Manchester have studied a specific group of stars found near the centre of our galaxy, in particular those hosting planetary nebulae. When stars, such as the sun, are at the end of their life, they expel material into space, which creates a striking structure, usually in the shape of an hourglass, or butterfly. These ‘ghosts’ are called planetary nebulae. Despite the planetary nebulae being unrelated, having different characteristics and properties, formed at different times, and located in different places, the study found a high degree of certainty that many of their shapes align in the sky in a similar manner. They are aligned almost parallel to the Galactic plane (our Milky Way)  - but the reason was unknown and the signal diluted. Until now. Led by HKU's MPhil student Shuyu TAN, the astronomers used additional data collected over the last decade to confirm that the alignment is exclusively present in planetary nebulae with close binary stellar companions - a star orbiting the main star at the center of the PNe in an orbit closer than Mercury's orbit around our Sun. Measurement of the equatorial position angle (EPA). The orientation axis measured from the projected 2-D image of a bulge PN was determined visually and the axis that best represents the long symmetry of each PN. The left panel shows a typical elliptical PN M 1-20 with a morphology of "Ems" and an EPA of 87° according to its major axis from HST observations. The right panel shows bipolar M 1-34 from our sample with a "Bps" morphology and an EPA of 31° measured from the VLT observation. Image credits: Shuyu Tan, The University of Hong Kong. The bulge distribution of measured GPAs for all PNe in the sample. The grey symbols are for the general sample while those PNe with confirmed binary central stars are blue vectors and those with high adfs (that are taken as a reliable proxy for PNe hosting short-period binaries) are pink vectors. M 1-34, suspected of hosting a short period binary, is plotted with a green vector. The usual name of each PNe are plotted under each blue, pink or green vector. Image credits: Shuyu Tan, The University of Hong Kong.   As the corresponding author of the paper and the Director of HKU Laboratory for Space Research, Professor Quentin PARKER, who is also a frequent and long-term visitor to Manchester University, suggests that these stellar companions could be the cause of this mysterious alignment. “The significance in this research lies in the fact that we now know that the alignment is solely observed in this very specific subset of planetary nebulae, those that host close binary central stars. This indicates the presence of a constant and controlled process that has influenced these objects over billions of years and vast distances. It is a remarkable discovery.” says Professor Parker. “Planetary nebulae offer us a window into the heart of our galaxy and this insight deepens our understanding of the dynamics and evolution of the Milky Way’s bulge region.” he adds. A now iconic collage showing 22 individual well-known PNe, artistically arranged in a spiral pattern by order of approximate physical size. Each nebula’s size is calculated from the SB-r statistical distance scale from Frew et al. (2016). It can be applied to PNe exhibiting the entire range of surface brightness, morphology and size. The largest PNe have a surface brightness about a hundred thousand times fainter than the smallest and can reach up to 3 pc across. General image credit: ESA/Hubble and NASA, ESO, NOAO/AURA/NSF from an idea by the corresponding author and Ivan Bojičić and rendered by Ivan Bojičić with input from David Frew and the author. Professor Albert ZIJLSTRA, a senior collaborator from Manchester University, said, “This finding pushes us one step closer to understanding this remarkable alignment.”  “The formation of stars in the bulge of our galaxy is a complex process that involves various factors such as gravity, turbulence, magnetic fields and interactions between particles. Until now, we have had a lack of evidence for which of these mechanisms could be causing this process to happen and generating this alignment.” he adds. The researchers investigated 136 confirmed planetary nebulae in the galaxy bulge – the thickest section of our Milky Way composed of stars, gas and dust - using the European Southern Observatory Very Large Telescope (a main mirror diameter of 8metres). They also re-examined and re-measured 40 of these from the original study using images from the high-resolution Hubble Space Telescope. They discovered that the alignment was found exclusively in planetary nebulae that host close binary central stars and that are also almost exclusively bipolars – planetary nebulae with a symmetrical shape. This suggests that the alignment is potentially linked to the initial separation of the binary components at the time of the star’s birth. The researchers also suggest that the binary stars may have been formed in the presence of a strong magnetic field, which could influence the axis of these planetary nebulae during their formation. Although further studies are needed to fully understand the mechanisms behind the alignment, the findings provide important evidence for a persistent, organised process that has influenced the formation and evolution of these planetary nebulae over billions of years. Click here to visit the website of HKU Laboratory for Space Research. Click here to view the journal paper.

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HKU Science Academics Achieve Top Honours in 2023 Best Scientists Rankings

The University of Hong Kong (HKU) has demonstrated its academic excellence by achieving outstanding recognition in the 2023 Best Scientists Rankings, developed by the globally recognised academic website, Research.com. Ten distinguished professors have been named the top 100 best scientists in their respective fields, including three Professors and two affiliated Professors from the Faculty of Science. In particular, Professor Guochun ZHAO, Chair of Earth Sciences, was ranked 10th in Earth Sciences globally.  Professor Xiang ZHANG, President and Vice-Chancellor of HKU and Chair of Physics, as well as Professor Guochun ZHAO have also achieved the top spot nationally as the number one ranked professors in China by discipline. Meanwhile, Professor Peng GONG, Chair of Global Sustainability at the Department of Earth Sciences has achieved the second position in China by discipline. The ranking is based on a scientist's D-index (Discipline H-index), which includes only publications and citation data for a specific discipline. The professors named the best scientists have made significant contributions to their respective fields and their work has had a significant impact on society. It is also a testament to HKU’s unwavering commitment to research excellence and innovation. This achievement will inspire us to keep pushing the boundaries of knowledge and continue making a positive impact on the world through our research.   Chemistry Professor Chi-Ming CHE (65th globally, 5th in China) Zhou Guangzhao Professor in Natural Sciences, Chair of Chemistry and Head, Department of Chemistry   Earth Science Professor Guochun ZHAO (10th globally, 1st in China) Chair Professor, Department of Earth Sciences   Professor Min SUN (18th globally, 4th in China) Professor, Department of Earth Sciences   Environmental Sciences Professor Peng GONG (70th globally, 2nd in China) HKU Vice-President and Pro-Vice-Chancellor (Academic Development) ; Chair Professor of Global Sustainability, Department of Earth Sciences   Physics Professor Xiang ZHANG (87th globally, 1st in China) HKU President and Vice-Chancellor; Chair of Physics, Department of Physics

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MicroSpine with Shape-Transforming Properties for Targeted Cargo Delivery at microscale

In nature, it is common to find structures that combine both soft and hard material. These structures are responsible for diverse mechanical properties and functions of biological systems. As a typical example, the human spine possesses alternating stacks of hard bones and soft intervertebral discs, which is an essential architecture that supports the human body while maintaining body flexibility.Mimicking the soft-hard structure in nature can, in principle, inspire the design of artificial materials and devices, such as actuators and robots. However, the realisation has been extremely challenging, especially at the microscale, where material integration and manipulation become exceedingly less practical. With the goal of advancing biomimetic microscale materials, the research team led by Dr Yufeng WANG from the Department of Chemistry of The University of Hong Kong (HKU) has developed a new method to create microscale superstructures, called MicroSpine, that possess both soft and hard materials which mimic the spine structure and can act as microactuators with shape-transforming properties.This breakthrough, published in the top scientific journal Science Advances, was achieved through colloidal assembly, a simple process in which nano- and microparticles spontaneously organise into ordered spatial patterns. Many biological organisms, ranging from mammals to arthropods and microorganisms, contain structures of synergistically integrated soft and hard components. These structures exist in different lengths, from micrometres to centimetres, and account for the characteristic mechanical functions of biological systems. They have also stimulated the creation of artificial materials and devices, such as actuators and robots, which change shape, move, or actuate according to external cues.   Microscale spine-mimicking structure, MicroSpine, has been created via colloidal assembly of soft and hard components, which can change shape by controlling temperature and can be utilised for cargo encapsulation and delivery. Image Credit: Dengping Lyu   Although soft-hard structures are easy to fabricate at the macroscale (millimetre and above), they are much harder to realise at the microscale (micrometre and below). This is because it becomes increasingly challenging to integrate and manipulate mechanically distinct components at smaller scale. Traditional manufacturing methods, such as lithography, face several limitations when attempting to create small-scale components using top-down strategies. For example, low yield can occur because small-scale manufacturing processes are more complex and require greater precision, which can increase the risk of defects and errors in the final product. To tackle the challenge, Dr Wang and his team took a different approach, called colloidal assembly. Colloids are tiny particles 1/100 the size of human hair and can be made from various materials. When properly engineered, the particles can interact with one another, spontaneously assembling into ordered superstructures. As a bottom-up method, colloidal assembly is advantageous for making microscale structures because it allows for precise control over the creation of the desired structures from various building blocks, possessing a higher yield. Yet, the difficulty is how to guide the particles to assemble to the desired soft-hard structure. By using the spine as a basis for design, the team has invented new particles derived from metal-organic frameworks(MOFs), an emerging material that can assemble with high directionality and specificity. Being also the hard component, these MOF particles can combine with soft liquid droplets to form linear chains. The hard and soft components take alternating positions in the chain, mimicking the spine structure, that is, the MicroSpine. ‘We also introduce a mechanism by which the soft component of the chain can expand and shrink when MicroSpine is heated or cooled, so it can change shape reversibly,’ explained Ms Dengping LYU, the first author of the paper, as well as the PhD Candidate in the Department of Chemistry at HKU. Using the MicroSpine system, the team also demonstrated various precise actuation modes when the soft parts of the chain are selectively modified. In addition, the chains have been used for encapsulation and release of guest objects, solely controlled by temperature. The realisation of these functions is significant for the future development of the system, as it could lead to the creation of intelligent microrobots capable of performing sophisticated microscale tasks, such as drug delivery, localised sensing and other applications.The highly uniform and precisely structured microscale components could be used to create more effective drug delivery systems or sensors that can detect specific molecules with high sensitivity and accuracy. The research team believes this technology represents an important step towards creating complex microscale devices and machines. According to Dr Wang, ‘If you think about modern machinery such as cars, they are assembled by tens of thousands of different parts. We aim to achieve the same level of complexity using different colloidal parts.’ By taking inspiration from nature, the research team hopes to design more biomimetic systems that can perform complex tasks at the microscale and beyond. Title of the Journal Paper: Biomimetic Thermoresponsive Superstructures by Colloidal Soft-and-Hard Co-Assembly, Science Advances, 9, eadh2250 (2023). DOI:10.1126/sciadv.adh2250 Click here to view the Journal Paper. The research is funded by the Research Grants Council (RGC). Learn more about Dr Yufeng Wang: Dr Yufeng Wang is an Associate Professor in the Department of Chemistry at HKU. As a material chemist, Dr Wang and his team specialise in designing anisotropic particles, which are the essential components for creating mesoscale materials with applications in photonics, sensing, micro robotics, cargo delivery, and active matter. Dr Wang’s research has been published in high-profile Journals including Nature, Nature Communications, Science Advances, JACS, Angewandte Chemie, etc. He has received the prestigious Croucher Innovation Award 2019, the NSFC Excellent Young Scientist Fund 2020, and the HKU Outstanding Young Research Award 2022. Dr Wang obtained his BSc degree from Peking University in 2008 and his PhD degree from New York University in 2013. Before joining HKU in 2016, he completed his postdoctoral training at MIT. More information about Dr Yufeng Wang’s research group: https://wanglab.hku.hk     

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Eminent HKU chemist Professor Hongzhe SUN receives the Royal Society of Chemistry’s 2023 Dalton Horizon Prize

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Potentially Producing Carbon-Neutral Fuels: HKU Chemists Achieve Sustainable Solar Energy Conversion with Artificial Photocatalysis

Converting solar energy into carbon-neutral fuels is a promising approach to reduce our dependence on fossil fuels and combat climate change. Taking examples from nature, plants and other photosynthetic organisms use sunlight to create energy-rich compounds from water and carbon dioxide (CO2) through a complex biochemical process that take places within specialised structures called chloroplasts. However, the efficiency of this natural process is limited by metabolic pathway that have a reflectively low effectiveness in converting sunlight into useful energy. While artificial photocatalytic cycles have demonstrated higher intrinsic efficiencies, they typically rely on pure or highly concentrated CO2 and organic media to prevent degradation of the catalyst caused by water or protons. Research teams led by Professor David Lee PHILLIPS from the Department of Chemistry of The University of Hong Kong (HKU), Professor Lili DU at Jiangsu University (HKU PhD Alumna), Professor Ruquan YE at the City University of Hong Kong and Professor Jia TIAN at the Shanghai Institute of Organic Chemistry have developed a remarkable and environmentally friendly system that can effectively harness light energy for the photocatalytic process. This artificial system is highly-stable and recyclable, and it does not rely on precious metals, making it more economically viable and sustainable. The research findings are recently published online in the top scientific journal Nature Catalysis. Background and Achievement In nature, organisms use a process called ‘hierarchical self-assembly’ to optimise light harvesting. During the process, they organise photocatalytic components within a tailored environment provided by lipid or protein-based scaffolds. By achieving high stability, selectivity, and efficiency, photosynthesis relies on the high surface area and precise spatial control of chromophore molecules and catalytic centres through self-assembly, which offers a design principle for highly efficient artificial photocatalytic systems. Recent studies have demonstrated using vesicles and micelles formed by co-assembly of natural lipids or synthetic surfactants with photocatalytic species. These structures act as micro-reactors, mimicking the environment of cell membranes. However, replicating the natural light-harvesting super complexes via synthetic pathways is hard to implement and far from cost-effective. With full appreciation for the current efforts and the challenges, the HKU team and their collaborators have designed a self-assembling artificial spherical chromatophore nanomicelle system in water inspired by the photosynthetic apparatus of Rhodobacter sphaeroides, a type of bacteria that is commonly found in soil and freshwater, which has a special structure called ‘spherical light-harvesting chromatophore’. This structure acts as a light sensor and possesses a remarkable ability to efficiently transfer energy from sunlight via a unique effect called ‘the spherical antenna effect’, created by circular arrangements of specific molecules on the surface of the chromatophore. This allows the bacteria to capture and utilise sunlight effectively for their energy needs. This artificial system mimics the bacteria's spherical light harvesting chromatophore and comsists of tiny spherical structures called nanomicelles that are self-assembled in aqueous solutions. These nanomicelles serve as the building blocks of the system. The system utilises modified molecules and light-absorbing compounds known as ‘aramid-linker enhanced Zn porphyrin amphiphiles’, which interact with a Co catalyst through electrostatic forces, leading to a unique hierarchical assembly. Hence, this assembly is induced by ‘spherical antenna effect’, and enhances the system to capture and alight energy for photocatalytic processes. The hierarchical self-assembly of the system offers a promising bottom-up strategy to create a precisely controlled artificial photocatalytic system with high stability and efficiency based on cheap and Earth-abundant elements rather than expensive precious metals. Professor David Phillips said: ‘Our research has the potential to advance renewable energy by replicating nature's efficient light-harvesting mechanisms. This could lead to sustainable solutions for our energy needs and the production of carbon-neutral fuels, contributing to a greener future.’ Professor Lili Du said: ‘The self-assembling artificial system is a significant step towards unlocking the full potential of solar energy conversion. Improving photocatalytic efficiency and stability can overcome limitations and create a cleaner, more sustainable energy landscape. This research offers promising practical applications in fuel production, carbon capture, and environmental remediation.’ About Professor David Lee Phillips Professor David Lee Phillips is a Chair Professor in the HKU Department of Chemistry. As an internationally recognised chemist, he uses time-resolved spectroscopy experiments and quantum mechanical calculations to study short-lived intermediates in chemical reactions of interest in chemistry, biology and the environment. He has published more than 400 internationally refereed scientific journal articles listed in Science Citation Index. He serves on the Editorial Advisory Board of the journal Molecules and also on the Advisory Board of the Journal of Physical Organic Chemistry. Professor Phillips graduated with a BSc from Iowa State University and with a PhD from the University of California, Irvine. Click here for more information about his research group.  About the Research Team Professor Jia Tian from the Shanghai Institute of Organic Chemistry, Professor Lili Du from Jiangsu University, Professor David Lee Phillips from the University of Hong Kong and Assistant Professor Ruquan Ye from City University of Hong Kong are the co-corresponding authors. Mr Junlai Yu and Libei Huang from Professor Tian’s Group are the co-first authors. Professor Ian Manners from the University of Victoria and other researchers (including Qingxuan Tang, Shang-Bo Yu, Qiao-Yan Qi, Jiangshan Zhang, Danying Ma, Yifei Lei, Jianjun Su, Yun Song, Jean-Charles Eloi, Robert L. Harniman, Ufuk Borucu, Long Zhang, Minghui Zhu, Feng Tian) from Shanghai Institute of Organic Chemistry and University of Victoria contribute to this project. Journal title: ‘Artificial spherical chromatophore nanomicelles for selective CO2 reduction in water’ (Nature Catalysis , 2023)  The journal paper can be accessed here.

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Bridging a catalyst: HKU chemists developed a metal-free cocatalyst to promote facile oxygen reduction reaction by inducing the formation of key hydrogen bonds between surface species

Ceaseless efforts from extensive research are ongoing to establish a sustainable and reliable future energy source. Fuel cells are one of the promising technologies to promote switching from non-renewable sources to renewable ones. However, the sluggish oxygen reduction reaction (ORR) at the cathode hampers the overall electrochemical performance of a fuel cell by generating an unfavourable byproduct, which is H2O2. A research group led by Dr Edmund CM TSE from the Department of Chemistry at the University of Hong Kong achieved an important breakthrough toward dismantling the technological barrier of fuel cells. Specifically, the Tse group has developed a promising electrochemical cocatalyst that overcomes the kinetic hindrances of ORR. The study was published on ACS Catalysis in an article entitled 'Immobilization of a Molecular Copper Complex and a Carboxylate Terminated Cocatalyst on a Metal Oxide Electrode for Enhanced Electrocatalytic Oxygen Reduction.' A fuel cell cathode encounters challenges such as a high energy barrier for breaking the strong O=O bond and intertwined proton-coupled electron transfer (PCET) processes for ORR. Failure to solve these challenges could ultimately lead to the production of toxic H2O2. Introducing platinum as an electrocatalyst can partially address the kinetic issues by driving the four-electron four-proton ORR at a reasonable turnover rate but still with room for improvement. However, the rareness of precious metal has limited the practical usage of Pt, thus spurring the exploration of alternative pathways through developing non-precious metal-based catalysts. 'Copper is known as an earth-abundant transition metal that is used by nature in metalloenzymes to produce water exclusively without H2O2 generation.' Dr Tse recalled their initial design efforts. 'With these in mind, we have designed a bioinspired electrocatalyst featuring a Cu complex with dipicolylamine (DPA) ligand.' Dr Shihuai WANG, a postdoctoral scholar in the Tse laboratory and the co-first author of this study, fabricated fluorine-doped tin oxide (FTO)-coated electrodes with mesoporous nickel oxide (meso-NiO) nanoparticles via a Ni sol-gel solution method. 'Our scanning electron microscope images show spherical pores with diameters varied between 20-60 nm.' Dr Wang elaborated on the unique features of their hybrid electrodes. 'These pores allow substrates easy access to the catalytic centre with a sophisticated surface coverage of functional moieties at the interface.' A copper(II) complex of functionalized DPA (CuL) and a carboxylate-terminated (COO–) phosphonopropionic acid (PPA) were then co-anchored onto the metal oxide surface of FTO/meso-NiO with the help of the phosphonate terminal group on the DPA ligand. The electrochemical performance of the FTO/meso-NiO/PPA/CuL electrode in pH 7 phosphate buffer showed a catalytic current exceptionally higher than the control cases. Impressively, the FTO/meso-NiO/PPA/CuL electrode almost does not generate H2O2 byproduct. 'The dual-immobilizing scheme played a vital role in encouraging interactions between surface adducts to promote the favourable PCET route for O–O bond cleavage.' Dr Mo, another postdoctoral scholar in the Tse group, remarked on the sophisticated design of their heterogeneous electrochemical platforms. 'The on-surface synergistic effect facilitated hydrogen bond formation to boost the electrocatalytic activity and selectivity simultaneously.' The Tse research team further explored the relationship between proton-coupled electron transfer steps and solution pH. 'At pH 7, the terminus of PPA converts from a neutral carboxylic acid group into an anionic carboxylate group.' Xutao Gao, a PhD student in the Tse group, performed density functional theory (DFT) calculations (Figure 1) to understand the working principle of this newly discovered cocatalyst. 'The negatively charged group then enticed the intermediates to form interfacial hydrogen bonds, thereby lowering the ORR energy barrier and releasing H2O as the sole product.' Distinct from the comparative control systems, the carboxylate-terminated FTO/meso-NiO/PPA/CuL catalyst showed a particularly low energy barrier of 0.19 eV due to the formation of hydrogen bonds. By establishing a new paradigm in improving ORR activity and selectivity without direct modification of the non-precious metal catalyst structure, Dr Tse envisages that significant enhancement in fuel cell performance could be achieved via the inclusion of metal-free cocatalysts. This synergistic strategy is expected to be widely applicable to other green resourcification operations and clean energy catalytic processes. Journal title: 'Immobilization of a Molecular Copper Complex and a Carboxylate Terminated Cocatalyst on a Metal Oxide Electrode for Enhanced Electrocatalytic Oxygen Reduction' (ACS Catalysis, 2023 ) The research paper can be accessed from here.  Click here to learn more about Dr Edmund CM TSE’s group.  Click here to learn more about HKU-CAS Joint Laboratory on New Materials.  More research stories:  HKU Chemists Develop a Novel Laser-Assisted Method to Make Catalysts for Efficient Oxidation of Glycerol from Biodiesel into Fine Chemicals HKU Chemists Developed Nitrile-Based Proton Carriers for Enhanced Oxygen Reduction

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New Quantum Key Distribution Breakthrough Improves Communication Security

Quantum key distribution (QKD) uses quantum mechanics to generate and distribute cryptographic keys that cannot be intercepted or cloned, making communication extremely secure. It has attracted worldwide interest because it promises information-theoretical security, which is the ultimate goal of communication security. However, the sources and detectors in the system can have side channels, which are vulnerabilities that can be exploited by hackers to compromise security. Although detector side channels have been addressed, source side channels have remained a challenge until recently.  A research team led by Professor Hoi Kwong LO and Dr Wenyuan WANG of HKU Department of Physics has proposed a QKD scheme without any modulators, which removes a major source of side channels on QKD sources. This breakthrough opens up new research directions to improve the security of practical QKD systems, making them even more secure in the future. Their findings has recently been published in Physical Review Letters. Journal title: 'Fully Passive Quantum Key Distribution', (Physical Review Letters, 2023).  Click here to view the journal paper.     

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Undergraduate Alumna’s Research Discovers New Proxy for Methane Seepage Activities

Our undergraduate alumna, Rachel Wai Ching CHU, who majored in Ecology & Biodiversity and graduated in 2019, began investigating methane seepage during her final year of undergraduate studies at the School of Biological Sciences as part of the capstone requirement for her major.Under the supervision of Dr Moriaki YASUHARA from the School of Biological Sciences and The Swire Institute of Marine Science, this research has recently been published in the highly respected and prestigious peer-reviewed scientific journal Geology. The article, titled ‘Late Quaternary paleoceanography of Vestnesa Ridge, Fram Strait: Ostracode species as a potential indicator of cold seep activity’, explores the topic of methane seepage and its potential indicators. Geology has been published by the Geological Society of America since 1973 and is a leading journal in the field of earth science. An investigation on how Methane levels impact our environment Methane is a potent greenhouse gas and is often portrayed as a significant contributor to global warming and climate change. A large quantity of methane is trapped in the deep ocean under high pressure and low temperature. At different times throughout geological history, part of it was released into the water and then into the atmosphere, thereby changing the climate. The release of methane is called methane seepage. Rachel’s paper investigates the strength of methane seepage activities in the Vestnesa Ridge during the Late Quaternary using two paleo-proxies: ostracod assemblages and carbon isotopes in foraminifera. Ostracods and foraminifera are two sand-grain-sized animals used by palaeontologists as micro-fossils to study environmental changes in the past. The paper suggests that one of the ostracod species found, Rosaliella svalbardensis, to be an indicator of moderate methane release since it was only present during moderate methane release, absent when there is no methane release or the activity is too strong. By discovering a reliable proxy for methane seepage activities, researchers can learn more about past seepage activities and their impacts on climate and the ecosystem. From FYP to Published Research Moriaki and his team specialise in palaeontology, and Rachel started volunteering in the Yasuhara Lab during the summer of her second year of undergraduate studies. Her involvement continued until her graduation and the research on methane seepage began as her final year project as part of the capstone requirement for her major. This career-oriented capstone course is designed for students interested in pursuing a career in academia. It imitates the academic environment and requires students to complete a research project of their choosing under the supervision of one of the topmost professors at The University of Hong Kong. Rachel described the entire experience as transformative, she said, ‘Paleo-related studies are rare in Hong Kong, and our curriculum did not cover much about it. Therefore, I owe everything I know in this field to Moriaki and his team, who tirelessly taught me from the very basics. Rachel said the capstone course provided her with an opportunity to experience a research project from start to finish, ‘No matter how fancy or detailed the lectures are, they cannot compete with hands-on experience, from wet-sieving the samples and identifying the species to analysing the data and coming up with a paper. Without these valuable experiences, I would have never known about the existence of this often overlooked yet the wonderful field of palaeontology, let alone pursuing an MPhil in this area now.’   Visit the Yasuhara Lab's website here. Click here to learn more about HKU BSc Ecology & Biodiversity Major.  Journal Title: ‘Late Quaternary paleoceanography of Vestnesa Ridge, Fram Strait: Ostracode species as a potential indicator of cold seep activity (Geology, 2023)’ The journal paper can be accessed here.   Profile: Rachel Chu 2020 - Present  MPhil Student of Environmental Sciences, CUHK 2015 - 2019: Bachelor of Science majored in Ecology and Biodiversity with a minor in Marine Biology and Spanish, HKU  

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Let the Sun Work its Magic: Revolutionary Sunlight-Powered Catalyst Transforms Methane into Valuable Chemicals

In a concerted effort with collaborators from the University College London, Professor Zhengxiao GUO from the Department of Chemistry, The University of Hong Kong (HKU), and Professor Junwang TANG, now at the Department of Chemical Engineering, Tsinghua University, have jointly developed a highly active and selective catalytic material that can efficiently convert methane, a potent greenhouse gas, into formaldehyde, an essential chemical in a waste-free manner. This innovative material, derived from tungsten trioxide (WO3 catalyst), features a dual active site comprising copper and tungsten atomic species that work in tandem to ensure an effective and selective conversion process. The conversion process can achieve nearly 100% selectivity under visible light, which avoids unwanted byproducts and increase efficiency, making it an eco-friendly alternative to current production methods. The findings have just been published in the prestigious journal Nature Communications. Change the unchanged: methane conversion Methane, the principal component of natural gas, is a widely used carbon source for numerous chemicals. Nevertheless, it is also a potent greenhouse gas, with more than 70 times the global warming potential of carbon dioxide. The catalytic conversion of methane (converting methane into other chemicals), therefore, presents a tremendous opportunity for achieving net-zero energy and chemical supplies while simultaneously addressing environmental concerns. However, methane is an extremely stable molecule, making it resistant to activation, particularly under mild or ambient conditions. Thus, achieving high activity and selectivity in methane conversion is a significant challenge, and the selective activation of the intermolecular carbon-hydrogen bond is often considered by many chemists as one of the most elusive ‘holy grails’ in catalysis. Formaldehyde, on the other hand, is a high-volume commodity chemical with a market value of USD 8 billion, expanding at a compound annual growth rate (CAGR) of 5.7%. It is used in household, commercial, aviation, medical and automotive products and serves as a valuable precursor for melamine, urea-formaldehyde and phenolic resins, among others. Formaldehyde is also safely used in the manufacture of vaccines, anti-infective drugs and hard-gel capsules. Currently, it is produced through methanol oxidation-dehydrogenation using silver or metal-oxide catalysts at high reactor temperatures of over 500-600°C, resulting in substantial carbon dioxide emissions and energy penalties. Harnessing Sunlight to Convert Methane In their study, the team discovers a new way of turning methane gas into formaldehyde using sunlight. They found that a mixture of atomically dispersed copper and partially reduced tungsten species over tungsten oxide worked really well – the synergistic ensemble enabling exceptional photocatalytic methane conversion to formaldehyde under ambient visible light. The process exhibited nearly 100% selectivity and high conversion efficiency, significantly outperforming previously reported photocatalysts (with a turnover frequency, TOF = 8.5×106 μmol (HCHO)·g-1(cocatalyst)·h-1). Through mechanistic analysis, they figured out that the copper helped to move electrons around and create reactive molecular species while the tungsten helped to activate the methane gas. Specifically, the copper acted as electron acceptors and promoted photo-induced electron transfer from the conduction band to dioxygen, generating reactive hydroperoxyl radicals (HOO·). Meanwhile, the adjacent tungsten atom that had a partial positive charge functioned as hole acceptors. The preferred adsorption and activation site of water produced hydroxyl radicals and effectively activated methane to methyl radicals. The synergy of the adjacent dual active sites greatly enhances the overall efficiency and selectivity of the conversion process. This finding paves the way for further research and development of new photo-catalysts for a variety of chemical conversions, promoting more sustainable and efficient processes in the chemical industry. ‘Solar conversion of methane is highly desirable for both low-carbon and high-value-added chemical syntheses. However, product selectivity and production efficiency are key to success. This requires an in-depth understanding of the conversion mechanism, careful design of the catalyst, and complementary techniques to confirm its performance – a good case of multidisciplinary tasks that require strong collaborative dedication. That’s exactly what the team has managed to do - with much value-added outcome!’ remarked Professor Zhengxiao GUO, one of the corresponding authors of the paper. Journal title: ‘Nearly 100% selective and visible-light-driven methane conversion to formaldehyde via. single-atom Cu and Wδ+’ (Nature Communications, 2023) The journal paper can be found in here.   

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In Memory of Professor Tze Leung LAI

  Professor Tze Leung LAI, a distinguished alumnus of the Department of Mathematics at The University of Hong Kong (HKU) and a world-renowned statistician, passed away on May 21, 2023. He held the esteemed position of Ray Lyman Wilbur Professor at Stanford University. Professor Lai's contributions to mathematical statistics and sequential statistical analysis were of great significance, particularly in the development of a comprehensive approach to sequential tests of composite hypotheses. His work earned him numerous accolades throughout his career. Beyond his groundbreaking research, Professor Lai will be remembered for his mentorship and guidance to young statisticians, leaving an indelible mark on the statistics and scientific community. While his absence creates a profound void, his pioneering work and lasting legacy will continue to inspire generations of scholars. We extend our deepest condolences to Professor Tze Leung Lai's wife, Ms Letitia Chow, his two sons, two grandchildren, as well as his family, friends, colleagues, and students. They had the privilege of knowing and working alongside an exceptional individual whose brilliance and passion for statistics will be sorely missed. The full obituary written by Professor Patrick Tuen Wai NG from the Department of Mathematics can be found here.

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HKU holds Inauguration Ceremony for the New Cornerstone Science Laboratory

The laboratory of Professor Shuang Zhang, Chair Professor of the Department of Physics and the Department of Electrical and Electronic Engineering, the University of Hong Kong (HKU), has become the first New Cornerstone Science Laboratory (“the Laboratory”) at HKU.   The Inauguration Ceremony for the Laboratory was held on May 15. Professor Peng Gong, Vice-President and Pro-Vice-Chancellor (Academic Development), and Professor Shuang Zhang, HKU;  and Ms Wurong Wang, Vice President of Tencent, and Vice President and Secretary-General of the New Cornerstone Science Foundation, officiated at the ceremony.   The New Cornerstone Science Laboratory was set up by the New Cornerstone Science Foundation (“the Foundation”) as a platform for launching research work and academic exchange. Tencent established the Foundation in 2022 to provide long-term support for basic research with a funding of RMB 10 billion over 10 years. The New Cornerstone Investigator Programme (“the Programme”) is a non-profit and independent funding initiative which takes an innovative approach to encouraging basic research spearheaded by leading scientists. The Programme focuses on Mathematics and Physical Sciences, and Biological and Biomedical Sciences, and encourages interdisciplinary research between the two areas.   Professor Zhang has been named among the first batch of three leading scientists under the Programme. His research interests primarily focus on the topological phenomena of high-dimensional photon systems, photonic strong topological insulators, the impact of vacuum fluctuations on electronic transport in two-dimensional materials, and the realization of new electromagnetic media, such as Tellegen media, using metamaterials.   Professor Peng Gong congratulated Professor Zhang for being selected for the Programme. He said that HKU, which is 112 years' old, is a world-renowned university with the most comprehensive disciplines in Hong Kong.  It is a university with disciplinary advantages and characteristics. It has accumulated long-term advantages in basic research and innovation, and has cultivated generations of outstanding talents. It is the university with the most internationalised teaching staff in China. Especially since 2018, under the leadership of HKU President Xiang Zhang, the world's top scholars have been vigorously introduced, and Professor Shuang Zhang serves as an excellent example of the outstanding scholars recruited.    A briefing session for the Programme was held right after the Inauguration Ceremony. During the session, the Secretariat of the Programme gave a comprehensive introduction on project positioning, application requirements, and application methods.   Please click here for the Powerpoint slides on the briefing session of the Programme, and here for the video of the briefing session. (HKU Portal Login required for viewing the Powerpoint slides and video)

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Physical Chemists Develop Photochromic Active Colloids Shedding Light on the Development of New Smart Active Materials

In nature, the skin of cephalopods (animals with tentacles attached to the head) exhibits unparalleled camouflage ability. Their skin contains pigment groups that can sense changes in environmental light conditions and adjust their appearance through the action of pigment cells. Although intricate in nature, this colour-changing ability is fundamentally based on a mechanical mechanism in which pigment particles are folded or unfolded under the control of radial muscles.    Inspired by this natural process, a research team led by Dr Jinyao TANG from the Department of Chemistry at The University of Hong Kong (HKU), develops a novel wavelength-selective intelligent colloid system to achieve light-controlled multi-dimensional phase segregation in collaboration with scientists from Hong Kong University of Science and Technology and Xiamen University. The team forms dynamic photochromic nanoclusters by mixing cyan, magenta and yellow microbeads, achieving photochromism on a macro scale. This macroscopic photochromism relies on light-induced vertical phase stratification in the active microbeads mixture, resulting in the enrichment of coloured microbeads corresponding to the incident spectrum.    Unlike existing colour-changing materials, this new photochromic colloidal swarm relies on rearranging existing pigments rather than generating new chromophores in situ and is, therefore, more reliable and programmable. Their findings provide a simple method for applications such as electronic ink, displays, and active optical camouflage, representing a major breakthrough in the field of active matter. The research result is recently published in the prestigious academic journal Nature.   Self-actuated active particles are micro/nanoparticles that mimic the directional swimming of microorganisms in liquid. Recently, they have attracted significant attention in nanoscience and non-equilibrium physics and is being developed for potential biomedical applications. One of the main research objectives of active particles are to develop medical micro/nanorobots based on these particles for drug delivery and non-invasive surgery. However, the structure of active particles is very simple, and their driving mechanism and environment perception are significantly limited. In particular, the size and relatively simple structure of the individual micro/nano active particles restrict the complexity of implementing functions on their body. The challenge and key to realising the future application is how to make active particles with intelligent characteristics despite their simple structure.       Light-powered microswimmers, a type of self-actuated active particles, have been recently developed for the purpose of creating controllable nanorobot, which offers potential for biomedical application and functional novel materials as the swimmer activity, alignment direction, and interparticle interaction can be readily modulated with incident light. On the other hand, light not only induces photosensitive motion in microswimmers but also changes the effective interaction between particles. For example, photocatalytic reactions can change the local chemical gradient field, which in turn affects the movement trajectory of neighboring particles through diffusion swimming effect, resulting in long-range attraction or repulsion.   In this work, Tang’s team designed a simple wavelength-selective TiO2 active microbeads system based on their previous research on light-powered microswimmers. Upon photoexcitation, the redox reaction on TiO2 particles generates a chemical gradient, which tunes the effective particle-particle interaction. That is, the particle-particle interaction can be controlled by combining incident light of different wavelengths and intensities. TiO2 microbead with different photosensitive activities can be formed by selecting dye sensitisation codes with different spectral characteristics. By mixing several otherwise identical TiO2 microbeads species loaded with dyes of different absorption spectra and adjusting the incident light spectra, the on-demand particle segregation is realised.   The purpose of realising particle phase segregation is to control the particle aggregation and dispersion in liquid at both micro and macro levels. Effectively, this resulted in a novel photoresponsive ink by mixing microbeads with different photo-sensitivity that maybe applied to electronic paper. The principle is similar to the pigment clusters in the skin of cephalopods that can sense the light condition of the environment and change the appearance of surrounding pigment cells through their corresponding actions. ‘The research findings have contributed significantly to advancing our knowledge of swarm intelligence in artificial active materials and have paved the way for designing innovative active smart materials. With this breakthrough, we anticipate the development of programmable photochromic ink that could be utilised in various applications such as e-ink, display ink, and even active optical camouflage ink,’ Dr Jinyao Tang concluded.    Three-dimensional phase segregation and photochromic colloidal swarm.  a, The Illustration of spectral sensitive layered segregation in the ternary colloidal system, where different illumination spectra resulted in distinctive vertical stratification.  b, The 3D distribution of ternary colloidal particles as imaged by confocal microscope after red, green, and blue light illumination. The SQ2, LEG4, and L0 sensitized TiO2 colloids are represented in cyan, magenta, and yellow, respectively. Scale bar: 50 mm. c, Modified projector is used to project designed colour images.  d, Six colour blocks emerged on the surface of photochromic ink after 2 min exposure. Inset: the projected pattern. Scale bar: 2 mm. e, The university logo emerged on the surface of photochromic ink after 2 min exposure. Scale bar: 2 mm. f, Sequential patterning of the photochromic ink with different colour paintings with 2 min exposure. Inset: the original projected patterns. Scale bar: 2 mm.    Journal paper: ‘Photochromism from wavelength-selective colloidal phase segregation’ , Nature Link: https://www.nature.com/articles/s41586-023-05873-4   View the research video: https://youtu.be/3Ylodxllwvo   More information about Dr Jinyao Tang: https://tanglab.hku.hk   

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HKU Chemist Professor Xuechen LI Honoured with Chinese Chemical Society’s Contribution Award in Carbohydrate Chemistry

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Eminent Chemist Professor Vivian W W YAM Awarded the Bailar Medal in Recognition of Her Distinguished Achievements in the Fields of Inorganic Chemistry and Coordination Chemistry

Professor Vivian Wing Wah YAM, the Philip Wong Wilson Wong Professor in Chemistry and Energy and the Chair Professor of Chemistry, has become the first Asian and Chinese recipient of the Bailar Medal. Professor Yam was invited to deliver two Bailar Medal Lectures on 24 and 25 April at the University of Illinois Urbana-Champaign (UIUC). The Bailar Medal has been established for over fifty years, and is awarded every year to the scientist who has made distinguished contributions to the fields of inorganic and coordination chemistry worldwide. Previous awardees include Nobel Prize laureates. They are Professors Henry Taube (1983), Jean-Marie Lehn (1987), Robert H. Grubbs (2005) and Richard R. Schrock (2015). Other Bailar Medalists include Professors Fred Basolo (Northwestern University), Richard Holm (MIT; Harvard), Malcolm L. H. Green (Oxford University), Harry B. Gray (California Institute of Technology), Jack Halpern (University of Chicago), Stephen J. Lippard (MIT), F. Albert Cotton (Texas A&M), Michael Grätzel (Ecole Polytechnique Federale de Lausanne), Jacqueline K. Barton (California Institute of Technology), Omar Yaghi (University of California – Berkeley), etc., and Professor Yam is the first Asian and Chinese who has been bestowed with this prestigious award. The Bailar Medal and Lectures commemorate Professor John Christian Bailar, Jr., known as the father of American coordination chemistry and a member of the faculty at the University of Illinois from 1928 until his death in 1991. Professor Bailar served as President of the American Chemical Society (ACS) in 1959 and was in large part responsible for the founding of the journal Inorganic Chemistry in 1962. Professor Bailar is the recipient of the ACS Award for Distinguished Service to Inorganic Chemistry, Priestley Award (the ACS’s highest honour), Frank Dwyer Medal, Alfred Werner Gold Medal, Heyrovsky Medal, Ferst Award, Chernyaev Jubilee Medal, and many other honours. The award of the Alfred Werner Gold Medal demonstrated the esteem in which Prof. Bailar was held by coordination chemists throughout the world. Prior to the award to Professor Yam in 2023, all forty-eight Bailar Medalists had been mainly from the United States and European countries etc. Professor Yam's distinguished achievements in the fields of inorganic chemistry and coordination chemistry, as well as her significant contributions to the rational design and synthesis of novel luminescent organometallic molecular functional materials, made her the first Asian and Chinese scientist to receive this prestigious Bailar Medal. Professor Vivian Wing Wah YAM is the Chair Professor of Chemistry of The University of Hong Kong and a world-renowned chemist. She was elected to Member of the Chinese Academy of Sciences (CAS) in 2001 at the age of 38 as the youngest member of the CAS, Foreign Associate of the US National Academy of Sciences, Fellow of the TWAS, Foreign Member of Academia Europaea and Founding Member of The Hong Kong Academy of Sciences. She is the Laureate of 2011 L'Oréal-UNESCO For Women in Science Award. She has received a number of awards, including the Josef Michl ACS Award in Photochemistry, Porter Medal, Royal Society of Chemistry (RSC) Centenary Medal, RSC Ludwig Mond Award, Inter-American Photochemical Society (I-APS) Presidential Award, Japanese Photochemistry Association (JPA) Honda-Fujishima Lectureship Award, JPA Eikohsha Award, Japan Society of Coordination Chemistry (JSCC) International Award, State Natural Science Award, CCS-China Petroleum & Chemical Corporation (Sinopec) Chemistry Contribution Prize, CCS Huang Yao-Zeng Organometallic Chemistry Award, Ho Leung Ho Lee Foundation Prize for Scientific and Technological Progress, APA Masuhara Lectureship Award, Fulbright Distinguished Scholar, Croucher Foundation Senior Research Fellowship, etc. She currently serves as the Chief Editor for Chemistry of Natural Sciences, a flagship open science journal of Wiley. She was an Associate Editor of Inorganic Chemistry of the ACS for 12 years from 2008-2020. She is currently the President of the International Organization for Chemical Sciences in Development (IOCD) (2022-) founded at UNESCO in 1981 to promote the pursuit and application of the chemical sciences for sustainable development and economic growth, as successor to the Presidency of Professor Glenn Seaborg, the inaugural President, and Professor Jean-Marie Lehn. She also serves as the Vice President of the Chinese Chemical Society (CCS), Chair of the CCS Committee for Women Chemists, and was the President of the Asian & Oceanian Photochemistry Association (APA). She has published over 590 journal articles. Her research interests include inorganic and organometallic chemistry, supramolecular chemistry, photophysics and photochemistry, and molecular functional materials for sensing, optoelectronics and energy research. In addition to this, Professor Yam was invited to deliver the Dow Lecture at the California Institute of Technology on 20 April on this trip. This special lecture recognises speakers who have conducted outstanding research in organometallic, catalysis, or inorganic chemistry.

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Professor Wang YAO - Excitement as the Driving Force for New Discoveries

  Professor Wang YAO Chair Professor of the Department of Physics Research interests: Theoretical Condensed Matter Physics, Quantum Physics and Optical Physics Research achievements: Professor Yao and his team have reshaped the understanding of valley quantum degree of freedom in electronic systems, and opened the door to its versatile control in two-dimensional materials. While the potential impact on technology remains to be seen, their work marks an important step forward in this field. capturing the interest of the research community ． Uncovering new phenomena and controlling physical processes in novel ways is incredibly fulfilling.   What inspired you to pursue a career as a physicist? Physics has been my favourite subject since high school. I was very fortunate to have an inspiring physics teacher who taught me the subject. I participated in the National Physics Olympiad during my high school period, an experience that encouraged students to explore beyond what is taught in class, and eventually led me to choose a physics major in university. What challenges did you encounter at the beginning of your research career? Like everyone at the beginning of the tenure track, the challenge laid in the transition. Before, I worked with senior people as part of their team. Now, I have to build my own research team, find my own research projects, and establish visibility as an independent Principal Investigator on the international stage. My experiences on two different research fronts during PhD and postdoc helped me to find an interdisciplinary area across the condensed matter, quantum physics and optical physics. Luckily, the emergence of twodimensional atomic crystals provided a wonderful arena for my study. How do you find your passion in this field as well as maintain it? My passion for doing physics research comes from the excitement of discoveries from time to time. Discovering physical phenomena that are not known before, and being able to control physical processes in a way not possible before, is truly fulfilling. What are the biggest problems regarding current physics research? There are many big scientific problems that remain to be tackled. One grand challenge that can impact everyone’s life is to revolutionise the physics foundation of information technology. The rapid development of modern information technology in the past five decades has been based on the continuous scaling down of microelectronic devices that improve cost, performance and power. This trend, empirically summarised as the Moore's law, is coming to an end because of the intrinsic scale limit of silicon microelectronics, where quantum physics inevitably interferes with the functionalities at the nanoscale. The new era of innovation will be profoundly different, calling for new physics principles to encode and process information, e.g. using quantum degrees of freedom, and new matter platforms to host devices. The challenge is also a great opportunity for fundamental research. What advice would you give to teenagers who are interested in science? What would you say to encourage them? Be curious and be able to think outside the box. Keep an open mind and expose yourself to the various frontiers of modern science. This could be a golden time as acquiring information has never been as facilitated as today. With HKU’s commitment to research excellence, researchers are highly valued in the University. Can you tell us how HKU support your research? HKU has provided a great platform to develop my career. I have experienced a friendly and supportive working environment and atmosphere here. The resources, internally and externally, are ample to grow my research as a theoretical group. I find the recognitions received from the university very encouraging.    Selected Awards and Achievements 2018-2022 Highly Cited Researchers by Clarivate Analytics 2021 Xplorer Prize 2021 Nishina Asia Award 2020 Fellow of American Physical Society 2020 Croucher Senior Research Fellow 2014/15 Outstanding Researcher Award, HKU 2014 OCPA Achievement in Asia Award (Robert T Poe Prize) 2013/14 Research Output Prize (Faculty of Science), HKU 2013 Croucher Innovation Award 2012/13 Outstanding Young Researcher Award, HKU  

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Physicist Dr Yi YANG selected as Physical Science Fellow in 2023 Asian Young Scientist Fellowship

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From Classroom to Conference room: Student Delegation Driving Climate Action at COP27

  Mark Kong Wai CHEUNG ． A fourth-year student majoring in the Environmental Science ． Co-Founder of Network of Environmental Student Societies (NESS) ． Member of the UN Asia Pacific Youth Advisory Group on Environmental and Climate Justice  I was proud to see youth's ideas were taken into consideration and would make a difference in the wider context of the Global Goal on Adaptation. The world is grappling with a critical challenge in the form of climate change, and the future generations will bear its brunt. However, instead of feeling defeated, a group of students from HKU has taken up the mantle of climate action, and is leading the charge towards a more sustainable and just future. Mark CHEUNG, a fourth-year student from the School of Biological Sciences, and the leader among the student delegation, is making a remarkable impact through his unwavering efforts to promote climate justice at the Conference of the Parties (COP27) held last year.   Embarking on a Mission As a youth climate activist, Mark is dedicated to addressing the climate crisis and promoting climate justice. Recognising the lack of Asian youth representation in international forums, Mark took the initiative to encourage Hong Kong universities, including HKU, to send student delegations to COP. After putting in great effort to draft proposals, create promotional materials, and secure meetings with HKU management, Mark finally led the first university student delegation from Hong Kong to attend COP27 in November 2022. Representing East and Southeast Asian students who are often overlooked in international forums, the delegation aimed to make their voices heard and contribute to the global fight against climate change by pushing for more inclusive and ambitious actions. With prior experience from COP 26, Mark guided his fellow delegates to maximise their learning opportunities. He also played a role in crafting policy proposals, participating in bilateral meetings, and took notes of member states’ stance on certain topics during official negotiations. With a welcoming atmosphere and attitude, some negotiators and Sub-Committee were open to their perspectives and voices. They agreed to take their views into consideration during the next official meeting. Mark said, ‘I was proud to see youth’s ideas were taken into consideration and would make a difference in the wider context of the Global Goal on Adaptation.’ Navigates the Challenges of Climate Negotiations Young activists may become discouraged in their advocacy work, as it can involve making concessions and participating in discussions that often result in unfavourable outcomes. Despite these difficulties, the student group remained steadfast in their commitment to championing climate action. Mark focused on having informal chats and connecting with global professionals and youth fighting for the same values and goals, rather than solely working on the intergovernmental aspects at COP27. These encounters and exchange reminded Mark of the importance of applying a peoplecentric and right-based approach in generating climate policies and solutions, he said, ‘Human-beings are always a crucial part in the climate crisis, and the relations between local cultures and climate actions should not be overlooked in decision making and planning processes. It is essential to have a bottom-up approach in different layers of the society to try to achieve intergenerational and intersectional equity.’ Reaping the Rewards: Takeaways from the Trip The trip allowed the student group to immerse themselves in the global effort to combat climate change, and gained diverse perspectives and insights regarding the impacts of climate change on different communities. They returned home with newfound inspiration and a sense of responsibility to take action on climate change. As the world moves forward in the face of this crisis, the hope is that more young people like Mark, especially amongst our readers, will step up and take on the mantle of climate champions. Conference of the Parties (COP) The Conference of the Parties (COP) governs the UNFCCC. Representatives from 196 nations gather annually to review climate change progress and discuss solutions. Since its founding in Berlin in 1995, the COP has been the world's leading climate change forum. Countries debate their intentions to reduce greenhouse gas emissions, adapt to climate change, and finance the low-carbon economy at these gatherings. If you are interested in taking climate actions in Hong Kong or starting your sustainability journey, feel free to follow his organisation’s work for more: https://www.nesshk.org  

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From HKU to Cambridge: A Unique Opportunity to Study Science across Two Continents

  Rupert Long Hei KWAN Year 2 student at University of Cambridge under the Cambridge Natural Sciences Tripos majoring in Physics/ Year 3 student at HKU (Cambridge-Track) My experiences at HKU gave me a solid foundation in physics, making it easier for me to grasp new concepts and adapt to the learning style at Cambridge quick. The HKU-Cambridge Undergraduate Recruitment Scheme for Natural Sciences is an exclusive opportunity for Young Scientist Scheme (YSS) participants in Natural Sciences Disciplines to pursue their passion for science across two continents and access worldclass resources. After two years at HKU and two to three years at Cambridge, selected students can earn three to four degrees from HKU & Cambridge in four to five years. Rupert KWAN, a member of the scheme's first cohort, found the experience to be life-changing. He was captivated by Cambridge's atmosphere, but it was the academic experience that left the most profound impression on him. Rupert was challenged in ways he never thought possible, as he juggled a hectic schedule of coursework and research projects. Each term only lasted eight weeks, but the amount of material he covered was comparable to a full semester at HKU. Despite the challenges, Rupert found comfort in the supportive supervising system, where small groups of students worked closely with a supervisor to discuss complex problem sheets. He was able to ask questions and engage in lively discussions, leading to a deeper understanding of sophisticated physical concepts.   Rupert found ample opportunities to hone his research skills through practical sessions, report writing, and poster presentations in Cambridge's undergraduate laboratory courses. These hands-on classes allowed him to explore experiments aligned with his interests and build a solid foundation in both theoretical and experimental physics, benefiting his future research career. However, Rupert's success on the Cambridge Track would not have been possible without the rigorous training he received at HKU. He said, ‘The experiences and knowledge I acquired at HKU allowed me to build a solid foundation in physics, making it much easier for me to understand new concepts in the fastpaced lectures. This is probably why I adapted to the learning style at Cambridge quickly in my first term and continue excelling academically.’ As Rupert enters his final year as an undergraduate, he knows his academic journey is far from over. He is more determined than ever to become a renowned physicist and explore novel physics phenomena to further our understanding of the universe's building blocks. ‘The Cambridge-Track has driven me closer to realising my dream of becoming a researcher,’ he said with a bright smile, eyes sparkling with excitement. Tips from Cambridge-Track Students: Preparing for the Cambridge Interview For selected YSS students applying for the Cambridge-Track, the Faculty offers valuable preparation by offering mock interview opportunities with academics in their respective fields. According to Rupert, the test and interview at Cambridge are not excessively challenging. He worked on online physics problem sets for a few weeks before the interview to refresh his knowledge and get comfortable thinking like a physicist. Ruper t also emphasised that while Cambridge interviewers don't anticipate candidates to have extensive out-ofcurriculum knowledge, they do expect them to have a sound comprehension of what they have studied and apply it in different cases. What is YSS?  Young Scientist Scheme (YSS) provides outstanding students with ample early research experiences in 6901 BSc and 6688 Science Master Class Programmes. Click here for more details. 

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Science Students Won Gold Medal in Prestigious International iGEM Competition

A team led by HKU Science students won a gold medal in the International Genetically Engineered Machine (iGEM) Competition Grand Jamboree 2022. The iGEM competition requires teams to use synthetic biology to develop projects and solutions to current world problems, and the team's project, called 'AMPed,' focuses on using microalgae to produce a specific antimicrobial peptide, Cecropin B, to address the problem of antibiotic resistance.  The overuse of antibiotics has caused antibiotic resistance, and Antimicrobial Peptides (AMPs) are a more effective and efficient solution to fight against these pathogens. AMPs have broad-spectrum antimicrobial activities and do not cause resistance due to their low specificity. Microalgae are an ideal chassis to optimise the production of AMPs due to their low susceptibility to AMPs and the ability to sustain themselves. The team's success in areas such as wet lab work, science communication, and education earned them a gold medal, making it their third in HKU iGEM history.    Team Captains:  School of Biological Sciences, Faculty of Science: Vicera Christian Nelson TEJEDOR and Rita Xin Yue LIM Team members: School of Biological Sciences, Faculty of Science: Jegadishwar Ananda NATARAJAN, Clara Yuen Yi PUN, Louis Pak Hei YU, Kirndeep KAUR, Eugenia King Hin FONG, Sarah KHAN, Faye Feifei LONG, Kazi Sunanas UTSHA,  Department of Physics, Faculty of Science: Vismaya Rajeev PILLAI Department of Mathematics, Faculty of Science: Sathya Geetha BALAJI School of Biomedical Sciences, LKS Faculty of Medicine: Sneha BALASUBRAMANIAN, Tanvi FALODIYA Biomedical Engineering, Faculty of Engineering Angel Ka Hang NG   Team supervisor:  Dr Juan Diego GAITÁN-ESPITIA of the School of Biological Sciences, Faculty of Science Dr Edmund Tse of Department of Chemistry, Faculty of Science Dr Amy Tan of the Faculty of Engineering

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HKU Astrophysicists Reveal the Nature of Dark Matter through the Study of Crinkles in Spacetime

Most of the matter in the universe, amounting to a staggering 85% by mass, cannot be observed and consists of particles not accounted for by the Standard Model of Particle Physics (see remark 1). These particles are known as Dark Matter, and their existence can be inferred from their gravitational effects on light from distant galaxies. Finding the particle that makes up Dark Matter is an urgent problem in modern physics, as it dominates the mass and, therefore, the gravity of galaxies – solving this mystery can lead to new physics beyond the Standard Model. While some theoretical models propose the existence of ultramassive particles as a possible candidate for Dark Matter, others suggest ultralight particles. A team of astrophysicists led by Alfred AMRUTH, a PhD student in the team of Dr Jeremy LIM of the Department of Physics at The University of Hong Kong (HKU), collaborating with Professor George SMOOT, a Nobel Laureate in Physics from the Hong Kong University of Science and Technology (HKUST) and Dr Razieh EMAMI, a Research Associate at the Center for Astrophysics | Harvard & Smithsonian (CFA), has provided the most direct evidence yet that Dark Matter does not constitute ultramassive particles as is commonly thought but instead comprises particles so light that they travel through space like waves. Their work resolves an outstanding problem in astrophysics first raised two decades ago: why do models that adopt ultramassive Dark Matter particles fail to correctly predict the observed positions and the brightness of multiple images of the same galaxy created by gravitational lensing? The research findings were recently published in Nature Astronomy.       Figure 1: Illustration of gravitational lensing by a galaxy. Light from a more distant and reddish galaxy is bent by a more nearby and bluish galaxy, which acts like a natural cosmic telescope to magnify the more distant galaxy. In this instance, multiple images of the reddish galaxy are created, forming a reddish ring-like feature referred to as an Einstein ring around the bluish galaxy. Image credit: ALMA, L Calcada, Y. Hezaveh et al.             Dark Matter does not emit, absorb or reflect light, which makes it difficult to observe using traditional astronomical techniques. Today, the most powerful tool scientists have for studying Dark Matter is through gravitational lensing, a phenomenon predicted by Albert Einstein in his theory of General Relativity. In this theory, mass causes spacetime to curve, creating the appearance that light bends around massive objects such as stars, galaxies, or groups of galaxies. By observing this bending of light, scientists can infer the presence and distribution of Dark Matter – and, as demonstrated in this study, the nature of Dark Matter itself.   As illustrated in Figure 1, when the foreground lensing object and the background lensed object – both constituting individual galaxies in the illustration – are closely aligned, multiple images of the same background object can be seen in the sky. The positions and brightness of the multiply-lensed images depend on the distribution of Dark Matter in the foreground lensing object, thus providing an especially powerful probe of Dark Matter. Another assumption of the nature of Dark Matter In the 1970s, after the existence of Dark Matter was firmly established, hypothetical particles referred to as Weakly Interacting Massive Particles (WIMPs) were proposed as candidates for Dark Matter. These WIMPs were thought to be ultramassive – more than at least ten times as massive as a proton - and interact with other matter only through the weak nuclear force. These particles emerge from Supersymmetry theories, developed to fill deficiencies in the Standard Model, and have since been widely advocated as the most likely candidate for Dark Matter. However, for the past two decades, adopting ultramassive particles for Dark Matter, astrophysicists have struggled to correctly reproduce the positions and brightness of multiply-lensed images such as those shown in Figure 2. In these studies, the density of Dark Matter is assumed to decrease smoothly outwards from the centres of galaxies in accordance with theoretical simulations employing ultramassive particles. Figure 2: Examples of gravitational-lensed images observed with the Hubble Space Telescope. Left: 2M130-1714, in which the four bright and bluish points comprise the quadruply-lensed images of the bright nucleus of a background galaxy, such that the main body of the background galaxy is lensed and distorted into an Einstein ring. The Einstein ring encircles two yellowish galaxies comprising the foreground lensing galaxies. Image credit: NASA/ESA/Hubble/T.Treu/Judy Schmidt. Right: The Einstein Cross, comprising four bright points corresponding to the quadruply-lensed images of the bright nucleus of a background galaxy. The fifth point near the middle of the cross corresponds to the foreground lensing galaxy.  Image credit: NASA/ESA/STSci Beginning also in the 1970s, but in dramatic contrast to WIMPs, versions of theories that seek to rectify deficiencies in the Standard Model, or those (e.g., String Theory) that seek to unify the four fundamental forces of nature (the three in the Standard Model, along with gravity), advocate the existence of ultralight particles. Referred to as axions, these hypothetical particles are predicted to be far less massive than even the lightest particles in the Standard Model and constitute an alternative candidate for Dark Matter.  According to the theory of Quantum Mechanics, ultralight particles travel through space as waves, interfering with each other in such large numbers as to create random fluctuations in density. These random density fluctuations in Dark Matter give rise to crinkles in spacetime, as illustrated in Figure 3 below for the Dark Matter surrounding galaxies. As might be expected, the different patterns of spacetime around galaxies depending on whether Dark Matter constitutes ultramassive or ultralight particles – smooth versus crinkly – ought to give rise to different positions and brightness for multiply-lensed images of background galaxies, as illustrated in the same figure. Figure 3: Visualisation of smooth versus crinkly spacetime produced by different forms of Dark Matter around galaxies. Left: Dark Matter comprising ultramassive particles create a smooth curvature in spacetime, such that light from a distant lensed galaxy takes smooth paths around the foreground lensing galaxy. Right: Dark Matter comprising ultralight particles creates crinkly fluctuations in spacetime, such that light from a distant lensed galaxy takes chaotic paths around the foreground lensing galaxy. The multiple images of the background galaxy thus created are predicted to have different positions and brightness for the different forms of Dark Matter around the lensing galaxy, allowing astrophysicists to probe the nature of Dark Matter. In work led by Alfred AMRUTH, a PhD student in Dr Jeremy LIM’s team at HKU, astrophysicists have for the first time computed how gravitationally-lensed images generated by galaxies incorporating ultralight Dark Matter particles differ from those incorporating ultramassive Dark Matter particles. Their research has shown that the general level of disagreement found between the observed and predicted positions as well as the brightness of multiply-lensed images generated by models incorporating ultramassive Dark Matter can be resolved by adopting models incorporating ultralight Dark Matter particles. Moreover, they demonstrate that models incorporating ultralight Dark Matter particles can reproduce the observed positions and brightness of multiply-lensed galaxy images, an important achievement that reveals the crinkly rather than smooth nature of spacetime around galaxies. ‘The possibility that Dark Matter does not comprise ultramassive particles, as has long been advocated by the scientific community, alleviates other problems in both laboratory experiments and astronomical observations,’ explains Dr Lim. ‘Laboratory experiments have been singularly unsuccessful at finding WIMPs, the long-favoured candidate for Dark Matter. Such experiments are in their final stretch, culminating in the planned DARWIN experiment, leaving WIMPs with no place to hide if not found (see remark 2).’ Professor Tom BROADHURST, an Ikerbasque Professor at the University of the Basque Country, a Visiting Professor at HKU, and a co-author of the paper adds, ‘If Dark Matter comprises ultramassive particles, then according to cosmological simulations, there should be hundreds of satellite galaxies surrounding the Milky Way. However, despite intensive searches, only around fifty have been discovered so far. On the other hand, if Dark Matter comprises ultralight particles instead, then the theory of Quantum Mechanics predicts that galaxies below a certain mass simply cannot form owing to the wave interference of these particles, explaining why we observe a lack of small satellite galaxies around the Milky Way.’ ‘Incorporating ultralight rather than ultramassive particles for Dark Matter resolve several longstanding problems simultaneously in both particle physics and astrophysics,’ said Amruth Alfred, ‘We have reached a point where the existing paradigm of Dark Matter needs to be reconsidered. Waving goodbye to ultramassive particles, which have long been heralded as the favoured candidate for Dark Matter, may not come easily, but the evidence accumulates in favour of Dark Matter having wave-like properties as possessed by ultralight particles.’  The pioneering work used the supercomputing facilities at HKU, without which this work would not have been possible. The co-author Professor George SMOOT added, ‘Understanding the nature of particles that constitute Dark Matter is the first step towards New Physics. This work paves the way for future tests of Wave-like Dark Matter in situations involving gravitational lensing. The James Webb Space Telescope should discover many more gravitationally-lensed systems, allowing us to make even more exacting tests of the nature of Dark Matter.’  Remarks: The Standard Model of Particle Physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions — excluding gravity) in the universe and classifying all known elementary particles. Although the Standard Model has met with huge successes, it leaves some phenomena unexplained – e.g., the existence of particles that interact with known particles in the Standard Model only through gravity – and falls short of being a complete theory of fundamental interactions.              For more information, please check here.  Last chance for WIMPs: physicists launch all-out hunt for dark-matter candidate.  The journal paper can be accessed here: Subscription required  Online version.  Click here for more information about the research team of Dr Jeremy Lim. 

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HKU Biologists Reveal a Molecular Scissor that Cuts Chromatin Bridge and Prevents DNA Damages and Autoimmunity

A research team led by Dr Gary Ying Wai CHAN from the School of Biological Sciences at The University of Hong Kong (HKU), has revealed the function of a unique enzyme, ANKLE1. ANKLE1 acts on chromatin bridges that are trapped in the midzone of the dividing cells. By cutting these bridges, ANKLE1 prevents damage to the genetic material and stops the immune system from mistakenly attacking the body’s own cells. Understanding the mechanism by which chromatin bridges are cleaved during cell division is important for developing new strategies to prevent or treat diseases such as cancer and autoinflammatory disorders. The research is highly relevant to both cancer and autoinflammation and has recently been published in Advanced Science. Background During cell division, the DNA must be divided properly into the two new cells. However, errors can occur during this process, causing parts of the DNA to stick together and form structures called chromatin bridges. These bridges are like strings of DNA that connect two segregating masses of chromosomes in the new cell. As a result, they would inevitably be trapped in the middle of the cell division process. When chromatin bridges are trapped in the midzone, they will be broken by contractile forces mediated by the actin-myosin complex, which can lead to DNA damages and the formation of small nuclei called ‘micronuclei’, causing genome instability, a characteristic of many solid tumours and activating innate immune responses that contribute to autoinflammation. To investigate the alternative mechanism that cells employ to resolve chromatin bridges, our research team has recently discovered that ANKLE1, a unique endonuclease (enzyme), plays a crucial role in cleaving chromatin bridges at midbody during cell division, thus avoiding catastrophic breakage caused by mechanical forces. This alternative mechanism helps ensure proper DNA segregation and stability, which is important for preventing diseases such as cancer and autoinflammatory disorders. The role of ANKLE1 in preventing DNA damage and autoimmunity Previously, scientists identified an endonuclease called LEM-3 in Caenorhabditis elegans, a microscopic roundworm commonly used as a model organism in biological research. LEM-3 has been found to play a role in resolving chromatin bridges at the ‘midbody’, a structure that connects the two daughter cells during cell division. The midbody is eventually severed, a process known as abscission, which results in the complete separation of the two cells. To understand the cellular functions of ANKLE1, which is the human equivalent of LEM-3, the research team employed the CRISPR/Cas9 genome editing technology to delete the ANKLE1 gene in human cells. During which, the team finds that loss of ANKLE1 leads to increased formation of extended chromatin bridges, suggesting that cleavage of bridges by ANKLE1 prevents further stretching of the DNA. In the absence of ANKLE1, the persistent bridges would be eventually broken by the actomyosin contractile forces that separate the two daughter cells. This mechanical breakage induces massive fragmentation of DNA, resulting in the formation of micronuclei and DNA released into the cytosolic DNA, which can trigger immune responses and lead to inflammation. Importantly, loss of ANKLE1 not only induces DNA damage and genome instability, but also leads to a strong activation of cGAS-STING innate immunity. cGAS-STING pathway is a major innate immune defence system against pathogens by sensing the DNA present in cytosol. In the absence of ANKLE1, DNA fragments are readily generated upon bridge breakage and the resulting cytosolic DNA is mistaken to be pathogenic DNA. These results indicate that ANKLE1 plays roles in both maintaining genome stability and preventing autoimmunity. Research significance The research not only has made a key discovery of a mechanism utilising a midbody-tethered endonuclease (ANKLE1) as a ‘scissor’ to cut chromatin bridges to prevent genome instability, but also enhances our understanding about the link between chromatin bridges and innate immune responses. ‘More and more research data suggest that immune responses play important roles in determining the clinical outcomes of many of the traditional anti-cancer drugs,’ said Dr Gary Ying Wai Chan. ‘For example, the use of antimitotic drugs is a common strategy to treat solid tumours. However, whether the induction of immune responses due to the resulting chromatin bridges is partly responsible for the antitumor effect remains unclear. The link between chromosomal instability and innate immunity will definitely be an area of cancer research with tremendous promise for breakthroughs.’   The role of ANKLE1 in maintaining genome stability and preventing autoimmunity Image Credit: Dr Gary Ying Wai CHAN

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New Insights into Glucose Metabolism: Targeting ATP Synthase with Chromium (III) Nutritional Supplement for Improved Blood Sugar Control

Recently, a research team led by Professor Hongzhe SUN from the Department of Chemistry, Faculty of Science, The University of Hong Kong, has published a paper in Nature Communications. The researchers found that, chromium(III) (Cr(III)), a nutritional supplement, can enhance cells’ ability to metabolise glucose by regulating ATP synthase activity. This process improves mitochondrial deformation caused by high glucose levels and significantly boosts glucose metabolism in type 2 diabetic mice. To uncover the protein targets of Cr(III) and elucidate the molecular mechanism, the team has developed a fluorescent probe for detecting transient metal-protein interactions, achieving a high spatiotemporal resolution tracking of the Cr(III) proteome in HepG2 cells. This led to the identification of Cr(III)-binding proteins within cells. The team then revealed that Cr(III) replaces magnesium ions (Mg2+) in ATP synthase, reduces ATP synthase activity, and activates the downstream AMPK pathway, resulting in improved glucose metabolism. This study provides a novel concept for hypoglycaemic research. “Although Cr(III) compounds have long been used as a nutritional supplement for diabetes treatment, weight loss and muscle development, its protein target and mechanism of action remain concealed for over half a century. We used a novel fluorescent probe, along with other chemical biology approaches, to uncover the long-standing scientific problem of the biological chemistry of Cr(III) and discovered that Cr(III) targets ATP synthase to regulate glucose,” commented Professor Sun. Research Background Diabetes, a chronic metabolic disease with over 500 million patients worldwide, cause nearly 2 million direct deaths each year. Over 95% of diabetic patients suffer from type 2 diabetes mellitus (T2DM), which poses a serious threat to human health. The effect of Cr(III) on anti-type 2 diabetes has been extensively studied in animal models. Since the initial discovery that Cr(III) supplementation in rat diets increased blood sugar removal rates, Cr(III) has been widely used in nutritional supplements for diabetes treatment, weight loss and muscle development. In fact, it is the second best-selling supplement in US, just after calcium mineral. Despite its significance in food and nutritional science, chromium remains one of the least understood transition metals in the periodic table. For over half a century, the importance, pharmacological properties, and mechanisms of action of Cr(III) in human physiology have been debated. The originally conceived low-molecular-weight chromium(III)-binding peptide (chromodulin) has never been reproducibly identified. Cr(III) is widely believed to improve glucose metabolism, maintain normal blood sugar levels, regulate carbohydrate and lipid metabolism, and enhance insulin signaling. However, the underlying molecular mechanism remains unknown, and the bottleneck in uncovering such a molecular mechanism lies in the difficulty in identifying Cr(III)’s molecular targets in cells. These biomolecules are crucial for elucidating Cr(III)’s physiological and pharmacological effects, constituting the so-called “Holy Grail” of chromium biochemistry. To date, no proteins that directly bind Cr(III) have been identified in cells or tissues. Various controversial separation and detection methods often produce weak Cr(III) signals, which might be attributed to the dissociation of Cr(III) from its bound proteins. Currently, there is no suitable method for tracking Cr(III)-binding proteins in living cells. For metals that bind weakly or transiently to proteins, labeling metalloproteins with a small molecule fluorescent probe is beneficial for understanding their spatiotemporal distribution and functional regulation in living cells. Key findings Building on their previous work, the team synthesised a fluorescent probe for tracking and recognising Cr(III)-binding proteins in living cells. The probe consists of three parts: a fluorophore (coumarin derivative (AC), a metal chelating group (i.e. nitrilotriacetate (NTA)) and a photoactive crosslinking group (i.e. arylazide). Upon chelation with chromium (III), the probe enters the cell, subsequently binds its target proteins, and the arylazide group forms a covalent bond with Cr(III)-binding proteins (i.e. target poteins) upon ultraviolet light irradiation. This leads to fixing the Cr(III)-binding proteins in cells without dissociation during downstream purification. Using these probes, the team monitored the distribution of Cr(III)-binding proteins in living cells, and found that they were concentrated in the cells’ mitochondria. These proteins were identified in conjunction with two-dimensional gel electrophoresis and mass spectrometry. The researchers discovered that Cr(III) binds residues of Thr213 and Glu242 in ATP synthase’s active site, replacing magnesium ion (Mg2+), reducing ATP synthase activity, and leading to AMPK activation. The AMPK pathway then alleviates mitochondrial damage caused by high glucose and improves glucose metabolism. This mode of action was successfully verified in a mouse model of type II diabetes. This study addresses how Cr(III) improves hyperglycaemic stress at the molecular level for the first time. With the identification of multiple Cr(III)-binding proteins, this study also opens a new horizon for further investigation of the pharmacological role of Cr(III) in other diseases other than anti-diabetes, such as anti-neurodegenerative diseases and anti-aging new horizons. The reviewers speak highly of this work “It is an immensely important aspect of basic science and its implications for human health, and it is exactly what is needed: the identification of molecular targets, an endeavour that has met with rather limited success in the last 70 years. Chromium supplements are a huge market worldwide (sold for weight loss, and muscle building). With controversies about their mode of action, it is rather questionable gambling with our health. Thus, the work addresses a major health issue that needs to be carefully evaluated for either the protection of large populations or the benefit for them concerning antidiabetic actions of chromium(III). The authors address chromium biology with a new approach of chemical biology and an impressive number of biochemical, molecular biological, and animal experiments.” About the research team This study was done jointly by The University of Hong Kong, Eco-Environmental Research Center of the Chinese Academy of Sciences, and City University of Hong Kong. Dr Haibo WANG and Dr Hongyan LI (The University of Hong Kong), and Dr Ligang HU (Eco-Environmental Research Center) are the co-first authors of this paper. Other members of HKU Department of Chemistry participating in the research include Dr Yau-Tsz LAI, postgraduate student Ms Xueying WEI, Dr Xiaohan XU, Dr Zhenkun CAO, and Dr Yuen-Yan CHANG. Professor Aimin XU of HKU Li Ka Shing Faculty of Medicine, Professors Guibin JIANG and Professor Qunfang ZHOU of the Eco-Environmental Research Center of the Chinese Academy of Sciences, Professor Mingliang HE and Dr Qianya WAN of the City University of Hong Kong, and Associated PI, Dr Huiming CAO of Jianghan University. The Research Grants Council of Hong Kong, and the Health Research Fund and the Basic Research Seed Fund of the Food and Health Bureau of the Hong Kong SAR support this study. The research work was supported by the University of Hong Kong (Norman & Cecilia Yip Foundation and URC). About Professor Hongzhe Sun Professor Hongzhe SUN is the Norman & Cecilia Yip Professor in Bioinorganic Chemistry and Chair Professor of Chemistry at The University of Hong Kong. His research lies in metalloproteomics and metallomics, discovery of antimicrobial and antiviral agents, and inorganic chemical biology.  To view the research paper “Mitochondrial ATP synthase as a direct molecular target of chromium(III) (Cr(III)) to ameliorate hyperglycaemia stress”, please visit: https://www.nature.com/articles/s41467-023-37351-w

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HKU Biologists Determine the Evolutionary Age of Individual Cell Types Providing Critical Insights for Animal Development

A research team led by Dr Chaogu ZHENG from the School of Biological Sciences at The University of Hong Kong (HKU) has recently made a significant discovery about the evolutionary age of different type of cells in a small animal called Caenorhabditis elegans (C. elegans). By using single-cell transcriptomic data and refined phylostratigraphy, the team determines the transcriptomic age of individual cells, which means they are able to estimate the evolutionary origin of different cells based on the age of the genes expressed in the cells. Their findings shed light on the cellular basis of the ‘hourglass’ pattern of animal development, revealing significant variation in the transcriptome age of different cell types. These results also provide insights into the varying contribution of different cells and tissues to adaptation, and the evolutionary relationship among cell types. These findings offer new perspectives on the genetic mechanisms that drive the evolution of species and have been published in the leading multidisciplinary journal PNAS. Insights from Molecular Studies on Hourglass Model The embryos of all animals share similar morphology at the middle stage of embryonic development while having larger morphological divergence at earlier and later stages. This pattern is often referred to as the ‘hourglass’ pattern of development, meaning that all animal development experiences an evolutionarily conserved phase during mid-embryogenesis. Recent molecular studies have shown that embryos at the middle stage of embryogenesis express the oldest transcriptome, which means that the oldest and most conserved genes are used at this stage during gene expression. In contrast, younger genes are expressed in the earlier and later stages of embryonic development. This was discovered by analysing gene expression of the embryos in different developmental stages using a technique called phylostratigraphy, a method used to determine gene ages by comparing their sequences across different species. However, these studies are limited in that they could only determine the transcriptome age of the entire organism throughout development but not in individual cells or tissue. This limitation is significant because obtaining information about the age of genes expressed in specific cells and tissue is crucial for gaining a more detailed understanding of the evolution of developmental patterns among species, as well as the genetic mechanisms driving it. Additionally, it can shed light on how individual tissue and cells contribute to the ‘hourglass’ pattern, which is a crucial aspect of understanding how different organs and tissues contribute to the evolution and adaptation of the overall developmental process in animals. From Whole-Organism to Single-Cell Analysis To fill this knowledge gap, the research team studies the transcriptome age of the nematode C. elegans at the single cell level using RNA sequencing. They look at RNA expression from both whole embryos (or organism) and individual cells to gain a comprehensive understanding of how different genes are used during embryonic and larval development. The team first identifies a period of the oldest transcriptome during C. elegans mid-embryogenesis, which starts after gastrulation, a process that forms different germ layers in the embryo and continues into the early development of an organ. More importantly, the research team finds that in early embryos, certain cells used older genes than other cells. For example, cells that would later become the germline (which is responsible for passing on genetic information to offspring) use older genes than somatic tissues in the body. Similarly, cells that would later become the endoderm (which gives rise to the digestive tract) use older genes compared to other cell types during early development. Among differentiated cells, muscles appear to have the oldest transcriptome than other cell types. It is also observed that the variation in transcriptome ages among the cell and tissue types remain small in early embryonic stages and grow bigger at late embryonic and larval stages as cells differentiate. Tracking the dynamics of transcriptome age along lineages identifies certain tissues, such as the skin, that contribute to the rise of the transcriptome age in late embryos. Further analysis of the variation in transcriptome ages among the 128 different types of neurons in C. elegans nervous system reveals that a specific group of chemosensory neurons and their downstream interneurons express very young transcriptomes, which may have contributed to adaptation in recent evolution, as many newly evolved young genes are associated with sensing environmental factors. Finally, by analysing the variation in transcriptome age among the different neuron types, as well as the age of the genes that regulate their development (fate regulators), the research team is able to hypothesize about the evolutionary history of some of these 128 neuron types. ‘Using C. elegans as an example, we showcase how the transcriptome age at the single-cell level can provide insight into the cellular basis of developmental innovation and help understand the functional diversity and evolutionary origin of cell types,’ said Dr Fuqiang MA, a Postdoctoral Fellow of HKU School of Biological Sciences and the first author of the paper. Dr Zheng, the supervisor of the research project, highlighted that ‘this study serves as an example of using the cutting-edge single-cell transcriptomics to study old problems in evolutionary biology.’ Dr Zheng envisions that the possibility of determining the evolutionary age of individual cell types at the transcriptome level can open up new research directions and advance our understanding of the genetic mechanisms that drive the evolution of species. About the research paper:  Ma F, Zheng C. Transcriptome age of individual cell types in Caenorhabditis elegans. Proc Natl Acad Sci U S A. 2023 Feb 28;120(9):e2216351120. doi: 10.1073/pnas.2216351120. The journal paper can be accessed from here:  This work is supported by funding from the National Science Foundation of China, the Research Grant Council of Hong Kong, and The University of Hong Kong.

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Dr Yi YANG recognised as one of the MIT Technology Review's Innovators Under 35 (China)

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In Memory of Professor Ming-Chit LIU

With great sorrow, we lament the passing of our esteemed former Chair Professor, Ming-Chit LIU (廖明哲), who departed from this world on 24th March 2023 at the age of 85. He is survived by his wife Ms Moon-Chi CHEUNG and two sons Kay-Wai LIU and Yun-Wai LIU.   Professor Liu dedicated more than thirty years of his life to The University of Hong Kong (HKU). After obtaining his BSc (Special) from the University in 1966, he joined the Department of Mathematics at HKU as a demonstrator. Simultaneously, he pursued his Master of Science degree under the guidance of Professor Yung-Ming CHEN. After completing his doctoral degree, Professor Liu was promoted to Lecturer in 1973 and continued his career at HKU. He was later promoted to Reader in 1983 and then to Professor in 1990. During his tenure, Professor Liu shifted his research interests from complex analysis to analytic number theory, particularly focusing on Diophantine equations and Diophantine inequalities involving prime numbers. His research on the well-known Goldbach conjecture set a new record in this challenging problem of number theory in 2002. He made significant contributions to strengthen the connections between the Department and external academic institutions.   Professor Liu taught first-year calculus for many years, delivering clear and well-organised lectures. Many students were fortunate to learn how to read and write epsilon-delta proofs from him. He also taught courses in number theory and postgraduate complex analysis, providing rigorous training in analytic number theory. In addition to serving on various departmental and university committees at HKU, Professor Liu also served on various review and selection committees for several local universities and the Hong Kong Government. For example, he served as Vice-President of the Hong Kong Mathematical Society from 1996 to 1998.   Professor Liu retired from HKU in 2000, and in 2005, the Department of Mathematics established the Liu Ming-Chit Prize in Mathematics with his generous donation. Currently, a team of five people working on number theory or closely related areas is maintained by the department.   Professor Liu will be dearly missed by the University and the Faculty of Science family. A full obituary of him by Professors Yuk Kam LAU and Patrick, Tuen Wai NG from Department of Mathematics can be viewed at: https://hkumath.hku.hk/web/memory/memory_mcliu_main.php 

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HKU Marine Scientist contributes to research assessing the potential risks of ocean-based climate intervention technologies on deep-sea ecosystems

The deep sea is one of the least well-known areas on Earth, comprising multiple vulnerable ecosystems that play critical roles in the carbon cycle. However, the deep sea is directly exposed to the effects of human-induced climate change and may now face additional challenges arising from efforts to counteract climate change artificially. These efforts have evolved into geoengineering solutions that could operate on vast spatial scales. Ocean-based climate interventions (OBCIs) are increasingly claimed as promising solutions to mitigate climate change. These interventions use different technologies to remove carbon dioxide (CO2) from the atmosphere and sequester the carbon in the deep sea, manage solar radiation, or produce renewable energy.  However, little is known about the impacts of OBCI technologies on ocean biogeochemistry and the biodiversity of ocean ecosystems. This is true in particular for deep-sea ecosystems, which cover over 40% of the Earth and contain highly vulnerable species and ecosystems. An international team of experts convened remotely as part of the Deep Ocean Stewardship Initiative’s Climate Working Group to consider the deep-sea impacts of OBCI. A research team led by Dr Lisa LEVIN from the Scripps Institution of Oceanography, UC San Diego, including Dr Moriaki YASUHARA from the School of Biological Sciences and The Swire Institute of Marine Science, The University of Hong Kong (HKU), has analysed the proposed approaches to assess their potential impacts on deep-sea ecosystems and biodiversity. Their findings were recently reported in the scientific journal Science raise substantial concern on the potential impacts of these technologies on deep-sea ecosystems and call for the need for an integrated research effort to carefully assess the cost and benefits of each intervention.  The research findings highlight the potential impacts of OBCIs on deep-sea ecosystems. Several lines of evidence led experts to raise substantial concern and call for the need for an integrated research framework to consider deep-sea impacts carefully in mitigation planning. Visual summary of OBCIs. Image credit: Sarah Seabrook. Balancing hope and risk While the growing interest in OBCIs as potential tools to mitigate the impacts may provide some hope for a sustainable future, the potential environmental impacts and effectiveness at full-scale have not been evaluated sufficiently. Additionally, governance of OBCI activities is also in the early stages, posing risks to deep-sea biodiversity and ecosystems. For example, one such intervention is direct CO2 injection into the deep sea, which could sequester large amounts of carbon dioxide from the atmosphere and reduce the overall concentration of greenhouse gases. However, while direct CO2 injection holds promise as a climate intervention, it also carries significant risks. One potential risk is the development of hypercapnia, a condition that occurs when the concentration of carbon dioxide in the water exceeds certain thresholds, which can have negative impacts on marine life and ecosystems. Other carbon sequestration technologies such as ocean fertilisation (enhancing phytoplankton production in the surface ocean and resulting their deposition on the deep ocean floor) and crop waste deposition (deep-sea disposal of terrestrial crop waste), the ideas putting carbon as phytoplankton or terrestrial plant bodies into deep-sea, could also change the food and oxygen availability for deep-sea life. The deep sea is facing unprecedented threats due to the impact of industrial fisheries, pollution, warming, deoxygenation, acidification and other climate-change-related problems. OBCIs could add further pressure and threaten the functioning of these systems, which are essential for the entire planet. The lead author Lisa Levin says, ‘I see open ocean-based climate intervention as a rapidly emerging arena that poses significant challenges for deep-ocean ecosystems, and thus demands new science and governance before we commit to action.’ ‘Especially given the vastness, vulnerability, comparatively pristine nature, and poor scientific understanding of the deep-sea ecosystem, we should be careful to green-light these activities that could have irreversible impacts.’ Moriaki Yasuhara continues. The interventions in the marine environment may be irreversible, and more research is needed to assess their impact. Prior to deploying geo-engineered solutions on a large-scale, we should at least understand what those pressures will be, and, by consequence, what the deep-sea may look like in the future. The journal paper can be addressed here A field of sea pens on a seamount off the Pacific Coast of Costa Rica. Photo credit:  Schmidt Ocean Institute, FK190106, Erik Cordes Chief Scientist.        

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Targeting DNA bridges: HKU Biologists Uncover key to preserve genome integrity Enhancing the understanding of cancer development

A research team led by Dr Gary Ying Wai CHAN from the School of Biological Sciences at The University of Hong Kong (HKU), has uncovered a new mechanism that ensures correct DNA segregation in cell division, where improper cell division will lead to the development of cancer. The team's findings, published in the journal Cell Reports, focus on the roles of two proteins, RIF1 and protein phosphatase 1 (PP1), in resolving ultrafine DNA bridges. These bridges are formed when sister chromatids are connected by DNA joint molecules during mitosis. If these DNA bridges cannot be resolved or removed properly, they will eventually break and cause DNA damage in the daughter cells, which can lead to the development of cancer cells. The process of Mitosis A human life begins with a single cell – the fertilised egg. This single cell needs to replicate and divide into approximately 37 trillion cells. The process by which a cell replicates its DNA then equally segregates into two identical cells is known as mitosis, which is a vital process for growth and replacing worn out cells. However, equal segregation of DNA is one of the most challenging tasks in mitosis. Our DNA is organised into 23 pairs of chromosomes, each of which is replicated into two sister chromatids. During mitosis, these sister chromatids are separated into two identical daughter cells. They are often connected by DNA joint molecules, which can form long fine DNA threads known as ultrafine DNA bridges when the two sister chromatids are separating under a pulling force. If these DNA bridges cannot be resolved or removed properly, they will eventually break, causing damage in the daughter cells. In a worst-case scenario, this DNA damage can potentially lead to the development of cancer. To elucidate the detailed mechanism of how cells resolve the DNA bridges, the team led by Dr Gary Ying Wai Chan uncovered the roles of two proteins, RIF1 and protein phosphatase 1 (PP1) in regulating the resolution of ultrafine DNA bridges. The role of RIF1 and PP1 in resolving DNA bridges In 2007, two research groups led by Professor Erich NIGG and Professor Ian HICKSON discovered the existence of ultrafine DNA bridges by identifying the first two ultrafine bridge-binding proteins, PICH and BLM. Later on, RIF1 was also identified as a bridge-binding protein. It is known that PICH is the first protein recognising the DNA bridges, then it recruits BLM and RIF1 to ultrafine DNA bridges; however, the exact mechanism by which these bridge-binding proteins work to resolve the bridges remains unclear. To understand the role of RIF1 in resolving DNA bridges, the research team employed a revolutionary genome editing technology, the CRISPR/Cas9, to deplete RIF1 in a cell model during mitosis. During which, the team found that loss of RIF1 leads to increased formation of DNA damage and micronuclei due to breakage of ultrafine DNA bridges, as our data suggest that RIF1 plays a crucial role in preventing double-stranded DNA bridges from converting into single-stranded DNA, which is more susceptible to breakage. RIF1 was found to achieve this by recruiting PP1, a protein phosphatase, which reduces the interaction between BLM and PICH and thereby reduces the amount of BLM on the bridges, which the team discovered that is responsible for unwinding the bridge DNA to single-stranded DNA. Finally, the double-stranded DNA bridges protected by RIF1-PP1 are believed to be resolved by another enzyme known as topoisomerase IIα, which could mediate double-stranded DNA decatenation to ensure proper DNA segregation. This research not only sheds light on the novel regulatory mechanism by which RIF1-PP1 facilitates the resolution of DNA bridges, but also reveals how ultrafine DNA bridges can induce DNA damage and genome instability if they are not properly resolved. The findings suggest that DNA bridge-binding proteins may serve as potential therapeutic targets for the development of anticancer drugs, as DNA bridges are considered a source of genome instability that drives tumorigenesis. ‘The discovery that RIF1 recruits PP1 to the bridges is the first step in understanding how the resolution of ultrafine DNA bridges is regulated by protein phosphorylation/dephosphorylation,’ said Dr Gary CHAN. ‘The next step is to identify the target substrates of the RIF1-PP1 complex, which can advance our understanding of how different bridge-binding proteins interact with each other and may lead to the identification of new therapeutic targets for cancer.’ The journal paper, entitled ‘RIF1 Suppresses the Formation of Single-Stranded Ultrafine Anaphase Bridges via Protein Phosphatase 1’, can be found here.  Click here to learn more about the work of Dr Ying Wai Chan and his research team.   

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Alumni Series - Tracing the Roots of Food with Stable Isotope Analysis

Food has always been fundamental to human life, connecting people to their roots, culture, and memories. As globalisation increases and food fraudulent concerns mount, tracing the journey of food from farm to table has become increasingly important. Faced with these challenges, two visionary PhD graduates from The School of Biological Sciences founded IsoFoodtrace, a company utilising stable isotope analysis, a food traceability technology, to provide a reliable and efficient platform for tracking food products’ origin and journey. IsoFoodtrace verifies food product attributes and labels, enabling unparalleled assurance in global food systems. By directly testing end products, their fast and cost-efficient methods allow consumers to know exactly what they buy. Let us explore the pioneering journeys of these young entrepreneurs driving unprecedented assurance in our food systems.   Dr Colin Luk and Dr David Baker. Meeting during their PhD studies in 2014, Inga CONTI-JERPE investigated coral nutrition using stable isotope analysis while Colin LUK studied forest recovery using Arthropods indicators. At that point, Colin had over ten years of F&B experience with concerns about food origin. He recalled, ‘I discussed using stable isotope analysis to detect food fraud with Inga, and we both think it’s doable. At the same time, HKU iDendron had just initiated a start-up SEED program while Science Park offered a 100K start-up grant—it seemed a good opportunity for us to build a start-up.’ With the support of Dr David BAKER, the Director of HKU Conservative Forensic Laboratory, and the consultation from Dr Jetty LEE, the Programme Director of the HKU MSc Food Industry: Management & Marketing, they piloted testing supermarket wild salmon and wrote a business proposal for funding, enabling them to launch IsoFoodtrace, a real business tackling food fraud.  Empowering Consumers to Make Informed Choices Dr Colin Luk at the Stable Isotope Laboratory of HKU Stable isotope ratios vary with food attributes like farming practices, feed, and origin. For example, wild salmon has more 15N (Nitrogen) than farmed, and cattle feed diets (grass vs grain) affect 13C (Carbon) ratios. Using Stable Isotope Ratio Mass Spectrometry, foods are chemically analysed and isotopes measured. Once the stable isotope signatures have been detected, they are then compared against a reference database; hence, the origin and composition of a food sample can be determined. This cutting-edge technology can ensure food safety and authenticity, giving customers peace of mind.. In just two years, IsoFoodtrace has grown to a team of 11. In the long term, it aims to build a global food stable isotope database enabling verification of production and origin claims. Colin said, ‘We aim not only to battle fraudulent claims of food quality but also to contribute to better food safety and sustainability by allowing businesses and consumers to make more informed purchases.’ Through their innovative approach to food tracing, they have revealed the complex processes involved in food production and distribution. Though now relocated to the US, Inga continues working with Colin to grow the business, she said, ‘Food safety is of paramount importance in today's globalised food systems. By tracing the roots of food, I hope we can eventually empower consumers to make informed choices and holds businesses accountable for authentic claims.’ As consumers, we can all play a role in supporting their efforts by seeking out products that have been verified and demanding greater transparency in the food industry. By doing so, we can help to build a safer and more sustainable food system for all.   Dr Colin Chung-lim LUK PhD in Biological Sciences Project Development Lead@isoFoodtrace     Dr Inga E. CONTI-JERPE Scientific Development Lead@isoFoodtrace Biological Researcher at University of California, Berkely                

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HKU biologists and collaborators reveal a gut-brain pathway that regulates sodium appetite

A research team led by Professor Billy KC CHOW from the School of Biological Sciences at the University of Hong Kong (HKU), in collaboration with Professor Li ZHANG, Guangdong-Hong Kong-Macau Institute of CNS Regeneration, Jinan University, has uncovered a new mechanism of the Secretin (SCT) in regulating water and sodium homeostasis, which demonstrates a gut-brain pathway that initiates sodium appetite and illustrates the function of colon released SCT. The study has recently been published in a top journal– Science Advances. Understanding sodium homeostasis in the body Water and salt homeostasis is one of the three fundamental homeostasis for mammals to maintain body metabolism. The disorder of water and sodium homeostasis will lead to hypernatremia and hyponatremia, leading to serious organ dysfunction, including muscles and the brain. Thus, sophisticated neural and endocrine pathways are formed to regulate water and sodium balance during evolution. Water and sodium homeostasis contain reabsorption, water consumption, and sodium appetite. The kidney controls peripheral water and sodium reabsorption mainly by the Renin-angiotensin-aldosterone system (RAAS), while water and sodium intake is tightly controlled in the brain. Circumventricular organs play vital roles in modulating water consumption, while the nucleus of the solitary tract (NTS) regulates sodium appetite. Compared with plenty of studies that have unravelled water intake regulation in the brain, only a few studies focus on neuron pathways that regulate sodium appetite. In the brain, HSD2-positive neurons in NTS and AT1a-positive neurons in the subfornical organ (SFO) initiate sodium intake separately, while the intestine and colon take responsibility for sodium uptake. Thus, understanding gut-brain cooperation will help in better constructing complete neural pathways. Through constant effort, our research team identified and confirmed a novel pathway that colon-released SCT activates NTS SCTR+ neurons, which project to the paraventricular nucleus of the hypothalamus (PVH) that takes responsibility for SCT-derived sodium metabolism. This study helps to better understand the peripheral-central cooperation that modulates sodium intake. Research Background SCT, a short peptide with only 27 amino acids, is the first identified hormone founded by William Bayliss and Ernest Starling in 1902, which regulates a wide range of systems in mammals, including gastrointestinal, cardiovascular, and central nervous systems. The SCT function is tightly connected to the SCT receptor (SCTR). As one of a class B GPCR, the signalling pathway of SCTR is closely connected with cyclic adenosine monophosphate (cAMP) and inositol triphosphate (IP3). The result from the human protein atlas shows SCTR has a high expression level in the respiratory system, GI tract, pancreas, and kidney. Some brain regions, such as NTS and the cerebral cortex, were also found SCTR expression. When acid chyme enters the duodenum, SCT is released to the bloodstream or intestinal lumen and detected by the pancreas SCTR. The pancreas then secretes pancreatic fluid full of bicarbonate, which neutralizes the acid from the stomach and protects the intestine. In the cardiovascular system, SCT and SCTR can regulate blood pressure, cardiac blood flow, and plasma NO concentration. In the central nervous system, SCT mediates motor learning behaviour, initiates water intake, and inhibits food intake. Key findings Here, we revealed a gut-brain pathway in which a gastrointestinal hormone, secretin released from colon endocrine cells under body sodium deficiency condition, is indispensable for initiating salt appetite. Peripheral SCT penetrates the blood-brain barrier and enters cerebrospinal fluid. As the neural substrate, SCT activates specific receptors in the NTS, which further project to the downstream paraventricular nucleus of the hypothalamus (PVH), resulting in enhanced sodium intake. These results demonstrated a previously unrecognized gut-brain pathway for the timely regulation of sodium homeostasis. Our results also have potential values in clinical fields, as ileostomy patients showed chronic salt and water disorders, together with low urinary sodium excretion, all of which are similar to the mice under sodium deficiency conditions. Such clinical observations can be replicated in animal models, as previous studies indicated SCT expression increased within 24 hours after colectomy and decreased significantly on day 14 in rats. Although no direct evidence has been provided for the role of colon-SCT in sodium homeostasis in human patients, these studies did imply its possible involvement. Further work can be performed to explore the possibility of targeting SCT-SCTR for correcting sodium imbalance in colectomy patients. The journal paper can be accessed here.   About the research team The research was conducted by the team led by Professor Billy KC Chow from HKU School of Biological Sciences. Dr Yuchu LIU from Professor Chow’s team is the first author of the paper. Professor Li Zhang is the co-corresponding author, and his team make a great effort in this study. The research has been supported by three grants from the Research Grants Council of Hong Kong and the National Natural Science Foundation of China. This study was supported by the Research Grants Council of Hong Kong GRF HKU17113120, HKU17127718, and the National Natural Science Foundation of China 32070955. About Professor Billy Chow Professor Billy K. C. Chow is the Chair of Endocrinology at the School of Biological Sciences, HKU. His expertise lies in GPCR and ligand interactions, eventually leading to deciphering the physiologic actions of GPCRs and identifying novel GPCR agonists/antagonists as therapeutic solutions. He is the founder of an HKU spin-off company PhrmaSec Ltd, which aims to translate basic research into societal impact by targeting GPCRs. 

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HKU Chemical Biologists decode a histone mark important for gene regulation program that go awry in cancer

A research team from the University of Hong Kong (HKU) led by Professor Xiang David LI from the Department of Chemistry in collaboration with Dr Yuanliang ZHAI from the HKU School of Biological Sciences and Dr Jason Wing Hon WONG and Dr Xiucong BAO from the HKU School of Biomedical Sciences (Figure 1) recently made a key breakthrough in understanding how genetic information encoded in our DNA is “read” and why errors in “reading” such information can often lead to developmental defects or cancers. The findings were recently published in Science. Each type of cell in the human body (with some exceptions) contains exactly the same DNA sequence known as genes. Therefore, to make a specific cell type (e.g., a stem cell, a neuron), each cell needs to carefully “choose” which genes to express. This fundamental process is regulated by diverse modifications of histone proteins, which were previously thought as mere spools for packaging DNA in the nucleus of our cells. We now know that these histone modifications are tags or marks on chromatin that function as master switches for the regulation of genes—they determine which sets of genes in a cell should be “ON” or “OFF” at the right time and to the right extent. Misregulation of this fundamental process underlies many severe human diseases such as cancers. Different types of histone marks act as cellular signals to control various chromatin-associated machineries that regulate gene expression, DNA replication, and damage repair. One of the challenges in chromatin biology is how particular histone marks are interpreted to achieve their biological function. To answer this question, it is essential to find the “readers”, a class of proteins that recognise specific histone marks and “translate” them by turning the expression of genes up or down accordingly. However, “readers” of many histone marks are still unknown, which limits our ability to understand their roles in gene regulation. A long-standing interest of Professor Li’s lab is the development of novel chemical approaches to identify histone “readers” that might be difficult to find using traditional biological methods. One such method uses a peptide containing a histone mark (i.e., a small fragment of histone protein) that acts as the “bait” to “fish” for “readers” that recognise the mark. ‘The key to success is not only the “bait” but also a specially designed “hook” that is equipped with a light-activated chemical group to capture the “readers” upon exposure to UV light,’ explains Professor Li.   In this study, the team focused on a methylation mark at histone H3 lysine 79 (H3K79me2). In human cells, this mark is found in actively expressed genes. Loss of H3K79me2 in mammalian embryos can lead to multiple developmental abnormalities, including impaired growth, cardiac dilation, and death. On the other hand, H3K79me2 has been found at abnormally high levels and in the wrong places (e.g., cancer-promoting genes) in a variety of cancers such as childhood leukaemia.  Despite its biological significance in gene regulation, the mechanism of how this mark is “translated” is unclear, as the “readers” of H3K79me2 have not been found since its discovery 20 years ago. In fact, over the years, many labs have tried various approaches to look for these “readers”. ‘It is a great challenge to identify H3K79me2 “readers”, even with our previously developed novel chemical approaches,’ says Professor Li. There are two major hurdles to overcome. First, “reading” the marks may involve not only the mark itself but also the whole histone and even the histone-DNA complex called a nucleosome. In other words, recognising H3K79me2 by its “readers” may require a native nucleosome- or chromatin-context. Second, the interaction between the “readers” and H3K79me2 can be weak or even transient and thereby easily lost during the “fishing” process. ‘To capture H3K79me2 “readers”, we must upgrade our “bait” and “hook”,’ says Li. But it was not trivial. Li's lab spent more than five years developing their new tool. Instead of using a small fragment of the histone protein, they chemically synthesised an intact nucleosome with an upgraded tri-functional “hook” and H3K79me2 as the “bait” (Figure 2). Using this new technology, the team successfully identified a protein called menin as the “reader” of H3K79me2. To understand how menin “reads” the H3K79me2 mark, the team adopted a cutting-edge technology called cryo-electron microscopy to visualise the molecular details of this interaction. ‘Unravelling the details of how menin binds H3K79 methylation is key to designing new drugs to treat cancers associated with misregulated H3K79me2’, says Professor Li. The pioneering work by Li and co-workers have advanced our understanding of the fundamental biological processes of gene regulation. These findings also open new opportunities for developing novel therapeutic agents to treat human diseases caused by abnormal levels of H3K79 methylation. The journal paper can be accessed here.  Click here to learn more about the research group of Professor Xiang David Li.    Figure 2. The research team chemically synthesised an intact nucleosome with an upgraded tri-functional “hook” and H3K79me2 as the “bait”. Using this new technology, the team successfully identified a protein called menin as the “reader” of H3K79me2. Image credit: Xiang David Li Group – The Laboratory of Chemical Epigenetics. 

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HKU neuroscientists discover a novel neural mechanisms of secretin receptor in regulating water intake, providing new ideas for solving hydromineral imbalance symptoms

Animals instinctively find and consume water when feeling thirsty in order to restore body fluid osmolality and plasma volume to their set points. The feeling of thirst is strongly influenced by the subfornical organ (SFO), a forebrain structure that integrates circulating signals, such as osmotic pressure and sodium contents, to stimulate thirst. While Secretin (SCT), a classical gastrointestinal hormone, has been implicated as a humoral factor regulating body-fluid homeostasis. As known that the mundane behavior of drinking water is actually governed by the complex neural mechanisms of SCT in the central nervous system, but how the signalling is involved in this process was unclear. Recently, a research team from the School of Biological Sciences (SBS) at The University of Hong Kong (HKU) collaborated with Jinan University and the Chinese University of Hong Kong (CUHK) to adopt a projection-specific gene deletion approach, demonstrating the neural mechanism for the first time, which reveals the important role of SCT Recepter (SCTR) in regulating drinking behaviour under thirst. This study not only expands the functional boundary of SCT, but also puts forward new insights into the regulation of the gut-brain axis in maintaining body fluid homeostasis, which provides new ideas for solving hydromineral imbalance symptoms (e.g., fatigue, headaches, arrhythmia, nausea, and vomiting etc.). Their findings have been published in the top journal Current Biology. The SFO located in the mammalian forebrain is the key site that regulates internal water balance, while SFO neurons are poised to receive signals about plasma osmolality, blood pressure, and hormones, which integrates these information to regulate thirst. Excitatory neurons in SFO are strongly activated under dehydration, and activation of such neurons can promote voracious water intake even under hydrated conditions. Previous studies focused on dissecting the neural circuits underlying thirst, but how peptide signalling is involved in this process still needs to be better understood. SCT was recently identified as a key factor that regulates body fluid homeostasis. Central and peripheral administration of SCT triggered water intake in rodents. Notably, the SCTR was also expressed in the SFO and is activated by SCT from blood circulation, suggesting that they may directly involve in body fluid balance dominated by SFO. To better understand the neural basis of how SCTR regulates thirst, the research team led by Professor Billy CHOW from HKU SBS, Dr Li ZHANG from Jinan University and Professor YUNG Wingho from CUHK jointly demonstrated that SCTR deletion in the SFO significantly reduces water intake in dehydrated mice. The team used electrophysiology and fibre photometry to show the SCT-SCTR axis participants in the activation of SFO excitatory neurons under dehydration. Moreover, they adopted a projection-specific gene deletion approach to demonstrate that SCTR participates in SFO to the median preoptic nucleus (MnPO) neurons pathway to regulate thirst. In short, this study reveals the important role of SCTR in regulating drinking behavior under thirst. SCTR may maintain normal drinking behaviour after thirst by regulating the membrane current changes of SFO excitatory neurons and mediating the neural excitability of the SFO to the MnPO pathway. This study provides a new perspective for understanding the role of gastrointestinal peptides in human body fluid homeostatic regulation. ‘Discovering the role of SCT in the central nervous system is exciting, but this is just the beginning, and our research is gradually expanding the role of SCT in the brain,’ says Professor Chow. ‘We will continue to follow the traces of SCT signals in the brain to descript a clearer neural mechanism.’ The journal paper can be accessed here. More information about Dr Billy Chow and his research group can be found from their group’s webpage. Professor Billy Chow (middle of the first row) and his research group.

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HKU biologists designed and developed novel anti-allergic drugs by targeting Mas-related G protein-coupled receptor (GPCR) X2 (MRGPRX2)

Allergic diseases are increasing at an alarming rate across the world. Despite available treatments, several cases of allergies are untreated and cause a huge disease burden. Moreover, allergies cause discomfort and life-threatening threats and can deprive one of taking life-saving vaccines. A research team led by Professor Billy K C CHOW from the School of Biological Sciences, Faculty of Science, the University of Hong Kong (HKU), have designed and developed novel small molecule MRGPRX2 antagonists which can be developed as novel anti-allergic drugs. This study has recently been published in The Journal of Allergy and Clinical Immunology (JACI). Research background In the area of allergy, previously, research on both mast cell degranulation and host response mechanism was focused on the IgE receptors (FcεRI)-mediated immune response. However, investigating the alternative non-IgE mechanisms of mast cell degranulation and allergic reactions has gained immense interest recently. Accumulating evidence on MRGPRX2 has shown its critical role in drug-induced allergic reactions, hypersensitivity reactions, and inflammatory diseases. Mast cells are tissue-resident innate immune cells, present predominately at exterior environment barriers, such as the skin and the respiratory tract. Mast cells are known for their densely packed secretory granules. On activation via activators (allergens, infectious agents, toxins, and drugs), mast cells can rapidly release these inflammatory mediators- this process is known as mas cell degranulation. This lead to allergies and inflammation of surrounding tissues or the whole body (See the diagram).   We have recently published a comprehensive review on the emerging role of Mas-related G protein-coupled receptor (GPCR) X2 (MRGPRX2) as a novel GPCR responsible for non-IgE mediated allergies and other inflammatory reactions. Several FDA-approved drugs, such as fluoroquinolone antibiotics, neuromuscular blockers, Icatibant, opioids, and diagnostic agents, have been reported to cause allergic and inflammatory reactions via MRGPRX2 activation.  Also, recently we have reported the mechanism of allergic reactions induced by a peptide P17 isolated from ant venom and the anti-allergic activity of the flavonoid compound genistein. In the current research, based on the lead structure (genistein), we have designed potent novel small molecule MRGPRX2 antagonists. These novel small molecule antagonists bind with MRGPRX2 (like a lock and key) and inhibit mast cell degranulation and release of inflammatory mediators; thus can be developed as novel ant-allergic drugs. Key findings We used a combined approach of structure-aided drug designing, virtual screening, medicinal chemistry, and experimental pharmacology, often used in big pharma for drug development. After screening thousands of molecules, we shortlisted six potent novel small molecules, designed the synthetic schemes and successfully synthesized and characterized them. These molecules are novel in structure and, to our best knowledge, have never been reported. Furthermore, we have screened these novel molecules via our well-established human mast cell model and mice models of acute and systemic allergies. Also, we have tested the anti-allergic potential of small molecules against FDA-approved drugs such as Fluoroquinolone antibiotic ciprofloxacin. The novel small molecule has shown a potent anti-allergic activity.  The societal impact of the findings The current state of research implies the crucial role of MRGPRX2 in non-IgE mediated allergic reactions, drug-induced allergies, pruritis, and inflammatory skin diseases. The current treatment strategies encompass mainly the symptomatic use of medications like anti-histaminic, corticosteroids, and monoclonal antibodies against IgE receptors. However, several cases of allergies are refractive to currently available treatments and fail to treat acute to severe cases. Moreover, no MRGPRX2-specific and effective drug is available in the market, indicating an unmet demand for drug development.  The research outcome from our project holds promising potential in the domain of mast cell biology and drug discovery and development as it has a direct pharmacological implication. The novel small molecule MRGPRX2 antagonist can be used as the experimental antagonist to understand the mast cells -MRGPRX2 mediated pathways and pathophysiology and can further be developed as a therapeutic drug molecule for the treatment of non-IgE mediated allergic reactions, itch, and inflammatory disorders. Based on the novelty and commercial impact of these small molecules, we have filed a US patent and a Chinese patent with the help of the technology transfer office of the University of Hong Kong. It is anticipated that our findings possess tremendous therapeutic and social impact. "Our translational research has opened a novel therapeutic area for treating chronic allergies," said Professor Chow. "I hope our efforts and others in this field will bring therapeutic solutions for chronic allergies in the coming years," said Dr Kumar. The research was conducted by the team led by Professor Billy K. C. CHOW(On the right). Postdoctoral fellow Dr Mukesh Kumar (on the left) from Professor Chow's group is the paper's first author.  Research Team The research was conducted by the team led by Professor Billy K. C. CHOW. Dr Mukesh Kumar (Postdoctoral fellow) from Professor Chow's group is the paper's first author. Dr Karthi Duraisamy from Prof Chow's group, Dr Rajasekar Reddy Annapureddy from Ludwig-Maximilians-Universität München, Germany and Dr Chi Bun Chan from the School of Biological Sciences, HKU are the other collaborator and contributed to the research. This research has been supported by the Hong Kong government RGC GRF 1711320, NSFC/RGC 17111421 and HKU seed fund for basic research 201910159222 and 104006152 to Prof Billy K. C. Chow.  About Professor Chow Professor Billy K. C. Chow is a Chair of Endocrinology at the School of Biological Sciences, HKU. His expertise lies in GPCR and ligand interactions, eventually leading to deciphering the physiologic actions of GPCRs and identifying novel GPCR agonists/antagonists as therapeutic solutions. He is the founder of an HKU spin-off company PhrmaSec Ltd, which aims to translate basic research into societal impact by targeting GPCRs.  The Journal can be accessed here. Click here for further reading.

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Catching the wrongdoers in the act: HKU chemists develop a novel tool to decipher bacterial infections in real time

A research team led by Professor Xiang David LI from the Department of Chemistry at The University of Hong Kong (HKU) has developed a novel chemical tool to reveal how bacteria adapt to the host environment and control host cells. This tool can be used to investigate bacterial interactions with the host in real-time during an infection, which cannot be easily achieved by other methods. The findings were recently published in a top-class international scientific journal — Nature Chemical Biology. Pathogenic bacteria, while only numbering fewer than a hundred, heavily threaten human health all over the world. For example, Mycobacterium tuberculosis infection causes tuberculosis, which leads to more than one million deaths each year. It was the world’s deadliest infectious disease until it was overtaken by COVID-19. Despite effective antibiotic treatments, multiple drug-resistant tuberculosis has become a growing problem worldwide. Therefore, a more comprehensive understanding of how bacteria infect their human host is key to developing new drugs and therapies. When bacteria meet their host (e.g., human cells), they send out ‘assassins’ (virulence factor proteins) that ‘hijack’ important protein players of the host to sow chaos during an invasion. Therefore, investigating which virulence factors bacteria secrete and which host proteins are targeted is crucial for the understanding of bacterial infections. However, it can be extremely challenging to identify these key players among the ‘crowded streets’ (excessive host cellular matrix). To tackle this challenge, Professor Li’s group designed a multifunctional unnatural amino acid called photo-ANA that only labels proteins of the engineered bacteria but not the host during infection. With the help of its alkyne handle, photo-ANA can conjugate with fluorescence or biotin via a Nobel prize-winning chemical reaction (‘click’ chemistry), which enables the visualisation and enrichment of the labelled bacterial proteins from the complex host environment. Thus, Photo-ANA serves as an ‘undercover agent’ to gather intelligence and tag all the ‘assassins’ sent by the bacteria. More importantly, photo-ANA also carries a diazirine group that can ‘handcuff’ the bacterial virulence proteins to their host target proteins upon exposure to ultraviolet (UV) light — cathing them in the act. Using photo-ANA, Professor Li’s group comprehensively profiled the adaptation of Salmonella, bacteria that can cause severe diarrhoea, to the host environment and revealed the extensive interplay between Salmonella and the host during different infection stages, which identified known interactions and some newly discovered interactions. Moreover, the photo-ANA-based approach can be easily applied to other pathogenic bacteria and even other pathogens such as fungi. With this new chemical tool, scientists can now investigate the activity of bacteria inside the host in real-time. In the future, this tool may help us decipher the hidden interactions of deadly bacteria with the host and the mechanisms of multidrug-resistant superbugs, which will further our understanding of infectious diseases and inspire new treatments. Link of journal paper can be accessed from here. 

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HKU Chemist and collaborators engineered an effective and stable singe-atom catalyst which is a hundred times more effective than the commercial catalyst

Developing a cost-effective electrocatalyst for green hydrogen generation from water is crucial for the development of renewable energy technologies to resolve the current energy and environmental crisis. In a concerted research effort, Professor Zhengxiao GUO from the Department of Chemistry at The University of Hong Kong (HKU) and his long-term collaborators in mainland China, have engineered an effective and stable ‘single-atom catalyst’ (SAC), with Pt single atoms supported on a vacancy-enriched dual metal hydroxide, (Co,Ni)(OH)2. This catalyst exhibits a far superior hydrogen evolution reaction (HER) activity, which is 116 times higher than that of the commercial 20 wt% Pt/C catalyst, even with a small fraction of the Pt loading. There is also negligible attenuation or degradation after the electrochemical test at 100 mAcm−2 for 24 hours or cyclic voltammetry for 20000 cycles, indicating the high stability of the catalyst, even at a relatively high current density for potential practical applications. The findings have just been published in Energy and Environmental Science. A sustainable clean energy supply is one of the foremost challenges to achieving ‘net-zero’ or carbon neutrality. Hydrogen is a promising clean energy carrier for such a purpose. However, its conventional production by methane reforming is accompanied by the generation of CO2 and also insufficient purity for the long-term operation of fuel cells. Using renewable power sources, such as solar or wind, is environmentally friendly for electrochemical water splitting to produce high-purity H2, which is increasingly important as the demand for hydrogen is likely to increase by 6-8 folds by 2050. However, this will create even more pressure on the already scarce Pt catalyst and its reserve. Moreover, the conventional cathode shows a relatively large overpotential and hence low efficiency (~60-80%) for H2 evolution, especially under alkaline conditions. Therefore, it is very desirable but challenging to develop a catalytic cathode that can efficiently evolve hydrogen at a relatively low overpotential under alkaline conditions. Despite considerable effort in the past, transition metal (TM) based catalysts usually show a relatively high overpotential and inferior catalytic performance to the commercial 20 wt% Pt/C, thus unfavourable for industrial applications. To date, Pt is still the most active candidate due to the moderate free energy for the chemisorption of atomic hydrogen, which is more advantageous than other metals for the formation of H2 via the intermediate Pt-*H (* denotes 'adsorbed'). Unfortunately, the HER efficiency depends not only on ΔGH but also on the dissociation of water to obtain *H and *OH and the subsequent transfer of the dissociated species. The direct water dissociation on Pt to form Pt-*H is usually sluggish under an alkaline condition, due to a relatively high water-dissociation barrier. Compared to the Pt nanoparticles and clusters, Pt Single-Atom Catalysts (SACs) show readily regulatable electronic properties and high atom utilisation efficiency (or atomic economy) for various reactions. Such single atoms can be stabilised and anchored on another material or substrate, such as TM oxides and hydroxides, to impart further the electronic synergy for catalytic performance. Particularly, TM hydroxides (e.g., TM = Fe, Ni, Co) are characterised by low-cost, good alkaline stability, high hydrophilicity and distinctive electronic structures with partially-filled d orbitals to facilitate interactions with charge carriers. However, the pristine TM hydroxides still exhibit low efficiency for the HER due to their relatively high adsorption energies of *H and/or *OH after water dissociation, unfavourable for *H diffusion to the Pt site and/or continued water adsorption due to *OH accumulation, respectively. In the combined electronic structural simulations and experimental analysis, the research team has identified that the bimetallic hydroxide of cobalt and nickel creates the electronic synergy for water dissociation with the 'just right' binding energies of *H and *OH to be transferred away from the hydroxide surface. Concurrently, the finely-tuned electronic microenvironment of Pt single atoms co-located over the (Ni,Co)(OH)2 substrate effectively reduced the energy barrier for hydrogen transfer on the (Ni,Co)(OH)2, to enhance hydrogen evolution. The generation of Ni-*OH and Co-*OH was directly observed by Operando Raman, indicating the enhancement of the (Co,Ni)(OH)2 for water dissociation in an alkaline electrolyte. Partial charge transfer from Pt to O atoms of (Co,Ni)(OH)2 creates an adequate local environment around the Pt, to attract the adsorbed *H species and then allow them to form hydrogen molecules with ease. In summary, this study opens up a new avenue for developing SACs via effective electronic tuning of Pt single atoms with heterogeneous atomic coordination in hydroxide substrates. More specifically, the catalyst demonstrated great potential to break the bottleneck of low efficiency for hydrogen generation in alkaline fuel cells, currently under popular consideration in large-scale electrolysis of water to produce clean fuels of the future. The journal paper can be accessed from here. 

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AFCD and SWIMS Enhance Collaboration in Managing and Disseminating Biodiversity Data

​The Agriculture, Fisheries and Conservation Department (AFCD) and The Swire Institute of Marine Science (SWIMS) of The University of Hong Kong entered into a Memorandum of Understanding (MoU) for enhanced collaboration in managing and disseminating marine biodiversity data.  The AFCD launched the HKBIH in March 2022 to provide a one-stop shop for information on local biodiversity. The forthcoming Biodiversity Geographic Information System (BGIS), which is expected to be launched in 2024 as part and parcel of the Hong Kong Biodiversity Information Hub (HKBIH), will facilitate the sharing of spatial data of local species. The AFCD and SWIMS endeavour to make the HKBIH a more comprehensive data repository to foster a better understanding and conservation of Hong Kong’s wealth of biodiversity. Information sharing is an important foundation of biodiversity conservation. Simon Chan, the Assistant Director (Conservation) at AFCD said the department will co-operate with SWIMS to share a vast amount of spatial data of local marine species with the public, via the BGIS of HKBIH. One of SWIMS’ main research directions is to continue building an up-to-date inventory of Hong Kong’s rich marine biodiversity. The Director of SWIMS, Professor Gray WILLIAMS, said he is delighted to collaborate with the AFCD to disseminate the information for public education and conservation initiatives.    Click here to learn more about HKBIH.  Click here to learn more about SWIMS. 

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Renowned Physicist Professor Shuang ZHANG was selected in Tencent’s New Cornerstone Investigator Program 2022

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HKU Marine Scientists discovered the reward and punishment system in coral-algae relationship

In human society, reward and punishment are introduced as an incentive to induce cooperation. However, some people still try to cheat to win. So, is there a system with clear rewards and punishments in the world of other organisms? The answer is ‘yes’. Corals may ‘punish’ the algae that live inside them by cutting off their food supply if such algae become selfish and renege on their part of the resource-sharing deal with the coral as part of their symbiosis – a mutually beneficial relationship. These are the findings of Dr Shelby MCILROY of the Swire Institute of Marine Science (SWIMS) and the School of Biological Sciences at The University of Hong Kong(HKU) and her collaborators.. In the coral-algae relationship, the two sides – the coral host, and the algal symbiont, share and recycle nutrients they cannot access on their own. But this relationship is open to abuse. Corals can host several species of symbiotic algae at the same time, but not all algal species are honest. Some take advantage of their host by keeping more nutrients for their own needs instead of passing them to the coral. In this way, the selfish algae gain an advantage over more beneficial species that grow slower because they share their nutrients more generously. This cheating ultimately undermines the long-term health and growth of the coral itself. In other symbiotic relationships, for example, between trees and fungi, the cheated hosts can interfere and punish their dishonest partners. However, until McIlroy’s latest research came out in the journal Microbiome, it has been difficult to determine if or how corals could do the same with their algae. Using stable isotope techniques, McIlroy was able to unravel the flow of nutrients between different species of algae in their host, a Caribbean coral species. ‘Stable isotopes combined with genetic techniques allow us to track the currency exchange between the partners. In this case, the currency is nutrients, in the form of carbon and nitrogen,’ McIlory explained. The results showed that the coral might indeed punish the cheats and reward the honest partners. ‘Our study showed that corals seem to limit the supply of nutrients to the symbiotic algae that are less beneficial to them, as a way of fostering more beneficial algal symbionts,’ McIlroy added. Understanding how corals control and manipulate their symbiotic algae is now crucially important for coral survival. Because of climate change, the seas are becoming too hot for the algae living inside the coral. When water temperatures spike, algae die, and so does the coral itself – a phenomenon known as bleaching. Episodes of bleaching are now becoming increasingly common, and most of the world’s coral reefs are now threatened by it. If scientists could get the coral to host the species of algae that can handle higher temperatures – a form of ‘coral probiotics’,  it could prevent bleaching and buy more time for corals threatened by the warming of the oceans. ‘We may have the ability to intervene and help corals resist bleaching by exposing them to more thermally tolerant partners. But we need to understand the biology of corals and how they might react to these interventions so that we can work effectively and efficiently. There’s no time to lose.’ McIlroy concluded. The journal can be accessed here. A video introduction to the research.

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Professor Billy Chow receives US National Academy of Medicine Health Longevity Catalyst Award (Hong Kong) 2022

Six research teams from The University of Hong Kong (HKU) were awarded the Healthy Longevity Catalyst Awards (Hong Kong) 2022 in the Healthy Longevity Global Competition, including the team of Professor Billy Chow from the School of Biological Sciences. The competition is held by the United States National Academy of Medicine (NAM) with the Research Grants Council as its Hong Kong sponsor. A total of ten research teams from Hong Kong were awarded this year. Launched in 2019, the Healthy Longevity Global Grand Challengeoffers opportunities for innovators, scientists, and entrepreneurs to catalyse breakthrough discoveries and innovations that could leapfrog existing barriers and jumpstart new solutions, thereby propelling the field of ageing research and improving the health of persons as they age. The competition composed three phases of Awards- Catalyst Award, Accelerator Award and the Grand Prize. The Catalyst Awards reward bold, new, potentially transformative ideas from fields such as biomedicine, behavioural science, sociology, engineering and infrastructure, technology, policy, to improve the physical, mental, or social well-being for people as they age, and in a measurable and equitable way. In particular, NAM seeks ideas that will extend the human health span through innovations in disease prevention, biology, mobility and function, social connectedness, productive longevity and more. Ideas could focus on early-, mid-, or late-life, as long as it ultimately promotes health as people age. Of the ten Catalyst Awards in Hong Kong this year, each includes a US$50,000 (approx. HK$389,000) cash prize at a maximum for a period of 12 months and travel subsidies (HK$30,000 per person; max. 6 persons per team) for awarded teams to attend an Innovator Summit in 2023. Project from the Faculty of Science: Development of Small-Molecule Modulators of the Secretin Receptor as Novel Anti-Hypertensive Agents Project leader: Professor Billy CHOW, Chair of Endocrinology, School of Biological Sciences, Faculty of Science About the project: Large segments of ageing hypertensive patients are resistant to a wide range of conventional drugs and hence there is an urgent need for new initiatives to develop alternative treatments. The research team developed the first small molecule-based Secretin receptor modulator (KSD179019), which not only has a similar blood pressure lowering effect as SCT peptide but, more importantly, has a much longer half-life (~8 hours). The development of KSD179019 as a novel class of oral anti-hypertensive drug can be of critical importance, as it could tackle resistant hypertension. This project could potentially provide an important advancement in finding novel small molecule drugs for resistant hypertension by targeting Secretin receptor. The Healthy Longevity Catalyst Awards (Hong Kong) 2022 Research Grants Council webpage The US NAM Healthy Longevity Challenge

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HKU biologists and collaborators reveal how DNA unzipping machine works, shedding lights on cancer therapy

A research team led by Dr Yuanliang ZHAI from the School of Biological Sciences, The University of Hong Kong (HKU), and his collaborators from The Hong Kong University of Science and Technology (HKUST) and Institut Curie, France, has uncovered a new mechanism of the human MCM2-7 complex in regulating replication initiation, which can be used as a novel and effective anticancer strategy with the potential for selective killing of cancer cells. The findings were recently published in the Cell journal. Human life begins with a single fertilised egg in the mother’s womb. This egg propagates through cell divisions and develops into our multicellular body. During each cell division, our genome DNA, the blueprint of genetic information, is accurately replicated. Each cell carries roughly 2 meters of DNA organised into 23 pairs of chromosomes. In our lifetime (~70 years), our body will synthesise more than a light year’s length of DNA of ~1016 meters - the distance light travels in one year. The replication process requires the DNA duplex to be first melted and then separated into two single-stranded templates for DNA polymerases to synthesise as complement strands. Any misregulation of this process can cause dire consequences, such as tumorigenesis and inherited genetic disorders. ‘Unlocking the secret of DNA replication is key to understanding the mystery of life.’ said Dr Yuanliang Zhai, Assistant Professor of HKU School of Biological Sciences, ‘Solving the structures of replication machines is central to inform their molecular functions as seeing is believing.’ Since 1953 when James WATSON and Francis CRICK determined the structure of DNA, how DNA duplex is initially melted has been a long-standing question for biologists. In eukaryotes, the enzyme responsible for unzipping DNA duplex during replication was originally identified as the minichromosome maintenance protein complex (MCM) genes from wine brewing yeast by our collaborator Professor Bik-Kwoon TYE at Cornell University in 1983. The products of six MCM genes, MCM2 to MCM7 (MCM2-7), form a six-subunit ring complex, serving as the catalytic core of the unzipping machine, the DNA replicative helicase. In cells, to initiate DNA replication, MCM2-7 complex must be first assembled into a head-to-head double hexamer (DH) encircling duplex DNA at thousands of places along each chromosome. Among a large reservoir of the assembled MCM2-7 DHs, only a subset of them will be finally selected and transformed into robust replicative helicases for DNA unwinding. It was believed that MCM2-7 DH could directly destabilise DNA to trigger an initial opening of duplex DNA. However, the underlying mechanism remained largely unknown. To address this question, the research team sought to use a cutting-edge technology, cryo-electron microscopy (cryo-EM), to visualise the atomic details of the MCM2-7 DH, which are almost millions smaller than the resolution limit of human eyes. In 2015, the team solved the first cryo-EM structure of MCM2-7 DH isolated from yeast at 3.8 Å, which was documented in the journal Nature. Unfortunately, the captured DNA was unstable and failed to inform the state of the DNA duplex bound by the MCM2-7 DH. Recently, the researchers successfully purified the MCM2-7 DH from cultured human cells and determined its structure at 2.59 Å. This high-resolution structure presents a clear picture of how the MCM2-7 complex destabilises DNA, giving rise to an initial opening of DNA duplex right at the juncture of the two coupled MCM2-7 hexamers. The team also found that the MCM2-7 DHs are loaded onto DNA at tens of thousands of sites across the human genome, which are mutually exclusive with loci of active transcription. Furthermore, when this initial open structure is disturbed, MCM2-7 DHs can no longer assemble onto DNA, leading to a complete suppression of DNA replication initiation. ‘The atomic-resolution cryo-EM structures enabled direct visualisation of the initial DNA melting, which is crucial for us to understand the molecular mechanism of DNA replication,’ said Dr Shangyu DANG, Assistant Professor of Division of Life Science, HKUST, ‘This study also demonstrates the importance of collaboration. Efforts from research groups with complementary expertise are required to answer the fundamental biological questions.’ DNA replication has been targeted by several therapeutic cancer drugs. However, the available drugs indiscriminately kill all dividing cells because both normal and cancer cells must replicate their DNA for cell proliferation. Thus, the specificity of these drugs raises serious concerns about these anticancer chemotherapies. A more desirable alternative is to inhibit DNA replication initiation so that normal cells will be arrested in the G1 phase (first growth phase) or withdraw from the cell cycle into the G0 state (resting phase); but cancer cells will undergo apoptosis. Therefore, inhibition of replication initiation can be used as a novel and effective anticancer strategy with the potential for selective killing of cancer cells. Our findings in this study provide high-resolution structural and mechanistic information on the human pre-initiation complex that can be used to develop nontoxic anticancer drugs using the MCM2-7 complex as targets in future. The journal paper can be accessed here.  About the research team: Led by Dr Yuanliang Zhai of the HKU School of Biological Sciences, the project was conducted by a team of international research groups: Dr Shangyu Dang from Division of Life Science (LIFS) of HKUST, Professor Bik-Kwoon Tye from Institute for Advanced Study (IAS) of HKUST, Dr Chunlong CHEN from Institut Curie, France and Qian ZHAO from Department of Applied Biology and Chemical Technology (ABCT) of Hong Kong Polytechnic University (HKPU). Co-authors include Mr Jian LI, Ms Xinyu FAN, Ms Yan Chit HUI, Dr Clare S. K. LEE and Dr Wai Hei LAM from School of Biological Sciences (SBS) of HKU; Dr Jiangqing DONG, Dr Daqi YU from LIFS of HKUST, Dr Weitao WANG and Mr Nathan ALARY from Institut Curie; Dr Yingyi ZHANG from Biological Cryo-EM Center of HKUST; and Mr Yang YANG from ABCT of HKPU. Learn more about Dr Yuanliang Zhai’s work and his research team. 

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Physicists develop a new method that strengthens electron-triggered light emission with flat bands Shedding light to produce new sources of light and build quantum-based computational and communications systems

The way electrons interact with photons of light is a vital part of many modern technologies, from lasers to solar panels to LEDs. But the interaction is inherently a weak one because of a major mismatch in scale: A wavelength of visible light is about 1,000 times larger than an electron, so the way the two things affect each other is limited by that disparity. Now, researchers at The University of Hong Kong (HKU), MIT and elsewhere say they have come up with an innovative way to make much more robust interactions between photons and electrons possible, in the process producing a hundredfold increase in the emission of light from a phenomenon called Smith-Purcell radiation. The findings have potential ramifications for both commercial applications and fundamental scientific research, although it will require more years of investigation to make it practical. The findings are just published in Nature, a prestigious multidisciplinary journal,  by Dr Yi YANG (Assistant Professor of the Department of Physics at HKU and a former postdoc at MIT), Dr Charles ROQUES-CARMES (Postdoctoral Associate at MIT), Professors Marin SOLJAČIĆ and John JOANNOPOULOS (MIT professors). The research team also included Steven KOOI at MIT’s Institute for Soldier Nanotechnologies, Haoning TANG and Eric MAZUR at Harvard University, Justin BEROZ at MIT, and Ido KAMINER at Technion-Israel Institute of Technology. In a combination of computer simulations and laboratory experiments, the team found that using a beam of electrons with a specially designed photonic crystal — a slab of silicon on an insulator, etched with an array of nanometer-scale holes — they theoretically predicted stronger emission by many orders of magnitude than would ordinarily be possible in conventional Smith-Purcell radiation and experimentally recorded a 100 times increase in radiation in their proof-of-concept measurements. Unlike other approaches to producing sources of light or other electromagnetic radiation, the free-electron-based method is fully tunable — it can produce emissions of any desired wavelength, simply by adjusting the size of the photonic structure and the speed of the electrons. This may make it especially valuable for making emission sources at wavelengths that are difficult to produce efficiently, including terahertz waves, ultraviolet light, and X-rays. The team has demonstrated the hundredfold enhancement in emission using a repurposed electron microscope to function as an electron beam source. But they say that the basic principle involved could potentially enable far greater enhancements using devices specifically adapted for this function. The approach is based on a concept called ‘flatbands’, which have been widely explored in recent years for condensed matter physics and photonics but have never been applied to affect the essential interaction of photons and free electrons. The underlying principle involves the transfer of momentum from the electron to a group of photons or vice versa. Whereas conventional light-electron interactions rely on a single mode of light, the photonic crystal is tuned to enable the production of a whole range of modes at the same frequency at once. The exact process could also be used in the opposite direction, using resonant light waves to propel electrons, increasing their velocity in a way that could potentially be harnessed to build miniaturized particle accelerators on a chip. These might ultimately be able to perform some functions that currently require giant underground tunnels, such as the 30-kilometer-wide Large Hadron Collider in Switzerland. ‘If you could actually build electron accelerators on a chip,’ Soljačić says, ‘you could make much more compact accelerators for some of the applications of interest, which would still produce very energetic electrons. That obviously would be huge, for example, for radiotherapy. For many applications, you wouldn’t have to build these huge facilities.’ The system could also be used to generate multiple entangled photons, a quantum effect that could be useful in creating quantum-based computational and communications systems, the researchers say. ‘You can use electrons to couple many photons together, which is a considerably hard problem if using a purely optical approach,’ says Yang. ‘That is one of the exciting future directions of our work.’ Much work remains to translate these new findings into practical devices. It may take some years to develop the necessary interfaces between the optical and electronic components and how to connect them on a single chip, and to develop the necessary on-chip electron source producing a continuous wavefront, among other challenges. ‘This is exciting,’ Roques-Carmes adds, ‘because this is quite a different type of source.’ While most technologies for generating light are restricted to very specific ranges of color or wavelength, and ‘it’s usually difficult to move that emission frequency. Here it’s completely tunable. Simply by changing the velocity of the electrons, you can change the emission frequency. That excites us about the potential of these sources. Because they’re different, they offer new types of opportunities.’ In order for the research outputs become truly competitive with other types of sources, it will require some more years of research. With some serious effort in two to five years, they might start competing in at least some areas of radiation. This article was adapted from the press release of MIT News Office. More details can be found in the article ‘Photonic flatband resonances for free-electron radiation’. 

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HKU biologists reveal the bioenergetics of pollen tube growth that sustain its rapid growth

  Sexual reproduction of plants requires pollen to land on the stigma, which then germinates and grows pollen tubes through the style to deliver sperm cells to the ovule. Pollen tubes are the fastest-growing plant cells known. Studies have shown that the growth rate of maize pollen tubes can reach up to 2.8 microns per second, while the growth rate of lily pollen tubes can also reach 0.2 to 0.3 microns per second. Its polarised growth process consumes a tremendous amount of energy, which involves coordinated energy fluxes between plastids, the cytosol, and mitochondria. Such an astonishing growth rate requires efficient and tremendous energy for metabolism and continuous synthesis of the plasma membrane and cell wall – the question is: where does the energy come from? A research team led by Dr Boon Leong LIM of the School of Biological Sciences at The University of Hong Kong (HKU) developed practical biosensors to measure real-time dynamic changes of energy currency in living plant cells and organelles, which reveals how Arabidopsis pollen tubes gain energy to sustain their rapid growth. Image 2. Model of the bioenergetics of Arabidopsis pollen tube growth. Image credit: Boon Leong Lim Unlike leaf cells, pollen tubes do not perform photosynthesis and mainly rely on sugar supply from the style to generate energy molecules such as Adenosine triphosphate (ATP), nicotinamide-adenine dinucleotide phosphate (NADPH), and nicotinamide adenine dinucleotide (NADH) to support pollen tube growth. Fatty acids (FA), the building blocks of the plasma membrane of the pollen tube, are synthesised in the pollen plastid, a precursor organelle of the chloroplast that does not contain chlorophyll. The synthesis of FA in pollen plastid consumes a large amount of ATP, NADPH, NADH, and acetyl coenzyme A(acetyl-CoA), an important metabolic intermediate. There are multiple possible routes of supplying ATP, NADPH, NADH, and acetyl-CoA for FA synthesis, but the exact mechanisms are obscure due to the small size of pollen tubes and the lack of tools to measure the concentrations of ATP, NADPH, and NADH in pollen plastids and the cytosol. The team led by Dr Boon Leong Lim recently published their findings in the journal Nature Communications, entitled ‘Bioenergetics of pollen tube growth in Arabidopsis thaliana revealed by ratiometric genetically encoded biosensors’. The team developed second-generation fluorescence NADPH and NADH/NAD+ ratio protein sensors and introduced these biosensors to the plastids and the cytosol of Arabidopsis pollen tube, thereby revealing the bioenergetics of pollen tube growth. By treating germinating pollen tubes with specific drugs, mitochondrial respiration was shown to be the main source of cytosolic ATP in Arabidopsis pollen tubes. Plastid ATP is mainly supplied by plastid glycolysis as well as importation from the cytosol through the nucleotide transporter (NTT) on the plastid membrane. As for the supply of plastid NADPH, the plastid malic enzyme NADP-ME4 is a more important pathway than the oxidative pentose phosphate pathway (OPPP). Although anaerobic respiration and pyruvate dehydrogenase (PDH) bypass are considered vital for supplying acetyl-CoA for plastid FA synthesis in tobacco pollen tubes, these pathways are not important in Arabidopsis pollen tube growth. Instead, plastid glycolysis is a more important source of acetyl-CoA for fatty acid synthesis. The conversion of NADH and NAD+ in plastids appears to be much more complex. While plastid glycolysis and plastid PDH pathway generate a substantial amount of NADH for FA synthesis, surplus NADH has to be converted back to NAD+ in pollen plastid by NAD-malate dehydrogenase (plNAD-MDH) to sustain plastid glycolysis. This research not only developed more practical biosensors to measure real-time dynamic changes of ATP, NADPH, NADH/NAD+ in living plant cells and organelles, but also reveals the exact biochemical routes of supplying ATP, NADPH, NADH, and acetyl-CoA for FA synthesis in pollen plastids. Ms Jinhong LIU, the first author of the article and a PhD student of Lim’s group remarked, ‘The in planta fluorescence protein sensors we developed are powerful tools for solving some key questions in plant bioenergetics. We are happy to publish two manuscripts in Nature Communications in 2022 (Note 1) on our discoveries using this novel technology’. Note 1: An HKU biologist-led team of international plant scientists reveals how guard cell chloroplasts obtain energy The journal paper can be accessed here.   

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