Applications from a single feedstock. A, Batch of as-cast, dried N63. B, Freestanding film of N63. C, N6360 spoon and fork. D, Demonstration of N6360 as a rigid spoon to scoop peanut butter. E, Demonstration of N6360 as a rigid fork to pick up a piece of cheese. F, Demonstration of N63110 as a pressure-sensitive adhesive. G, Demonstration of N6360 immediately failing as an adhesive. Credit: Science (2024). DOI: 10.1126/science.adi5009
A team of molecular engineers have developed a type of plastic that can be shape-shifted using tempering. In their paper published in the journal Science the team, from the University of Chicago, with a colleagues from the US DEVCOM Army Research Laboratory, Aberdeen Proving Ground, the National Institutes of Standards and Technology and the NASA Glenn Research Center, describe how they made their plastic and how well it was able to shape shift when they applied various types of tempering.
Haley McAllister and Julia Kalow, with Northwestern University, have published a Perspective piece in the same issue of Science outlining the work.
Over the past several years, it has become evident that the use of plastics in products is harmful to not only the environment but also human health—bits of plastic have been found in the soil, the atmosphere, the oceans, and the human body.
Consequently, scientists have begun looking for ways to reduce the amount of plastic that is created, used and dumped into the trash. In this new effort, the research team has created a type of plastic that can be converted to something new once its initial purpose has been exhausted—using tempering. A plastic bag holding food, for example, could be converted to a fork or spoon.
To allow for such shape-shifting, the researchers developed a type of plastic using a dynamic cross-linked approach that was based on the reversible addition of thiols to benzalcyanoacetates—a process known as a “Michael addition.” The resulting plastic was of a type that could be modified by tempering, which is where a material is heated to a certain point, then chilled quickly. Tempering is most often associated with metalwork.
The researchers found by that heating the plastic to temperatures ranging between 60°C and 110°C, then transferring it to a standard food freezer, they could create different objects from the same material based on a whim.
They created a spoon first, which they used to scoop peanut butter from a jar. They then used tempering to change the spoon to a fork, and then to an adhesive material capable of holding two panes of glass together. However, tests showed that there was a limit to the number of times the plastic could be changed, which was seven times. After that, it began to degrade.
by Gisela Olias, Leibniz-Institut für Lebensmittel-Systembiologie
Eva Bauersachs in the sensory lab. Credit: J. Krpelan, Leibniz-LSB@TUM
A research team led by the Leibniz Institute for Food Systems Biology at the Technical University of Munich has solved the mystery of a novel clove-like off-flavor in orange juice, the cause of which was previously unknown.
The study, published in Food Chemistry, proves for the first time that the undesirable flavor note is due to the odorant 5-vinylguaiacol. As the results of the study show, the substance is mainly produced during the pasteurization process when residues of a cleaning agent react with a natural orange juice component under the influence of heat.
This is not the first time that the orange juice industry has had to contend with clove odor. So far, 4-vinylguaiacol has been considered the main cause of this undesirable flavor note, which is particularly abundant in orange juices that have been stored for a long time. The quantitative determination of this odorant has therefore long been an established part of routine quality controls.
Eva Bauersachs, Ph.D. student at the Leibniz Institute in Freising and first author of the study, explains, “Recently, however, we have received reports of orange juice samples that had a pronounced clove odor despite a low concentration of 4-vinylguaiacol. We therefore asked ourselves which other odorants contribute to this undesirable off-flavor.”
On the trail of off-flavors
To investigate this question, the research group led by Martin Steinhaus, head of the Food Metabolome Chemistry research group at the Leibniz Institute, carried out extensive investigations in cooperation with the Professorship of Functional Phytometabolomics and the Chair of Food Chemistry and Molecular Sensory Science at the Technical University of Munich. The aim was to identify the odorants that cause the previously unexplained off-flavor and to elucidate their origins.
Using techniques such as gas chromatography-olfactometry and aroma extract dilution analysis, the team identified the odorant 5-vinylguaiacol as the source of the off-flavor in an orange juice with a pronounced clove odor. The presence of this substance in orange juice was previously unknown. Compared to 4-vinylguaiacol, it even proved to be more odor-active in five out of six commercially available orange juices with a clove-like off-flavor.
Further studies suggested that 5-vinylguaiacol is formed during pasteurization when the characteristic orange juice component hesperidin reacts with peracetic acid. Peracetic acid is used as a cleaning agent for cleaning-in-place (CIP) in the fruit juice industry, among others.
“Inadequate rinsing of the machines after the CIP process could therefore have led to contamination of the orange juice with peracetic acid and caused the formation of 5-vinylguaiacol during further processing,” says principal investigator Martin Steinhaus. Based on the new scientific findings, the team recommends that orange juice processing companies should no longer use peracetic acid as a cleaning agent.
Single-crystal x-ray analysis captures the two protons (bright yellow spots, top and bottom) moving between two positions on the molecule. Credit: Royal Society of Chemistry, CC BY 3.0 DEED
Chemists at RIKEN have developed a method for making synthetic derivatives of the natural dye indigo that doesn’t require harsh conditions. This discovery could inspire advances in electronic devices, including light-responsive gadgets and stretchy biomedical sensors.
Semiconductors based on organic molecules are attracting much interest because—unlike conventional rigid semiconductors based on silicon—they could be flexible, ductile and lightweight, opening up new possibilities for designing semiconductor devices.
Organic molecules also have the advantage of realizing a broad range of structures. “Organic semiconductors have flexibility in molecular design, enabling them to adopt new functionalities,” says Keisuke Tajima of the RIKEN Center for Emergent Matter Science, who led the research published in Chemical Science.
To explore this potential for enhanced electronic function through molecular design, Tajima and his team investigated a molecule related to indigo, called 3,3-dihydroxy-2,2-biindan-1,1-dione (BIT). “This project started with a simple question: Can protons and electrons move in concert in the solid state?” says Tajima.
Proton-coupled electron transfer—in which the motion of electrons is linked to that of protons—is often considered critical for realizing efficient electron transfer in biological systems. If it can be incorporated in organic solid-state materials, it could lead to semiconductors with unique dynamic properties. Until now, however, no solid-state material displaying proton-coupled electron transfer has been demonstrated.
Tajima and his team have now found that BIT and its derivatives undergo unusual rearrangements in their structures involving double-proton transfer, which may lend them unique capabilities as electronic functional materials.
Tajima identified BIT and its derivatives as promising materials for solid-state proton-coupled electron transfer, because the molecule incorporates two protons that appear ideally positioned to hop from one position to another during electron transfer.
Until now, making BIT required harsh conditions that severely restricted the range of derivatives that could be made. Members of the team developed a room-temperature approach that enabled the synthesis of several BIT derivatives under much milder conditions.
With BIT derivatives in hand, the team explored the molecules’ properties. “The most difficult part was to prove that the protons in BIT undergo proton transfer between molecules in the solid state,” says Tajima. In collaboration with RIKEN experts in X-ray crystallography and solid-state nuclear magnetic resonance (NMR), the team demonstrated that the two protons do rapidly exchange their positions.
Calculations suggest that proton transfer is indeed coupled with charge transport; the team’s next target is to confirm this coupling experimentally. “We don’t know if the presence of a proton will enhance charge transport, but as fundamental physics it could open interesting avenues,” says Tajima.
Design and characterization of piezoelectrically and topographically originated biomimetic scaffolds. (a) Schematic representation of the enhanced bone regeneration mechanism through electrical and topographical cues provided by HAp-incorporated P(VDF-TrFE) scaffolds. (b) Schematic diagram of the fabrication process. Credit: The Korea Advanced Institute of Science and Technology (KAIST)
Bone regeneration is a complex process, and existing methods to aid regeneration including transplants and growth factor transmissions face limitations such as the high cost. But recently, a piezoelectric material that can promote the growth of bone tissue has been developed.
A KAIST research team led by Professor Seungbum Hong from the Department of Materials Science and Engineering (DMSE) has developed a biomimetic scaffold that generates electrical signals upon the application of pressure by utilizing the unique osteogenic ability of hydroxyapatite (HAp). HAp is a basic calcium phosphate material found in bones and teeth. This biocompatible mineral substance is also known to prevent tooth decay and is often used in toothpaste.
This research was conducted in collaboration with a team led by Professor Jangho Kim from the Department of Convergence Biosystems Engineering at Chonnam National University. The results are published in the journal ACS Applied Materials & Interfaces.
Previous studies on piezoelectric scaffolds confirmed the effects of piezoelectricity on promoting bone regeneration and improving bone fusion in various polymer-based materials, but were limited in simulating the complex cellular environment required for optimal bone tissue regeneration. However, this research suggests a new method for utilizing the unique osteogenic abilities of HAp to develop a material that mimics the environment for bone tissue in a living body.
Analysis of piezoelectric and surface properties of the biomimetic scaffolds using atomic force microscopy. (a) PFM amplitude and phase images of box-poled composite scaffolds. The white bar represents 2 μm. (b) 3D representations of composite scaffolds paired with typical 2D line sections. (c) In vivo bone regeneration micro-CT analysis, (d) schematic representation of filler-derived electrical origins in bone regeneration. Credit: The Korea Advanced Institute of Science and Technology (KAIST)
The research team developed a manufacturing process that fuses HAp with a polymer film. The flexible and free-standing scaffold developed through this process demonstrated its remarkable potential for promoting bone regeneration through in-vitro and in-vivo experiments in rats.
The team also identified the principles of bone regeneration that their scaffold is based on. Using atomic force microscopy (AFM), they analyzed the electrical properties of the scaffold and evaluated the detailed surface properties related to cell shape and cell skeletal protein formation. They also investigated the effects of piezoelectricity and surface properties on the expression of growth factors.
Professor Hong from KAIST’s DMSE said, “We have developed a HAp-based piezoelectric composite material that can act like a ‘bone bandage’ through its ability to accelerate bone regeneration.” He added, “This research not only suggests a new direction for designing biomaterials, but is also significant in having explored the effects of piezoelectricity and surface properties on bone regeneration.”
The LipidOz software helps researchers process the complicated data obtained from their instruments and assigns the locations of double bonds in lipids. Repetitive and difficult analyses can be automated with LipidOz. Credit: Stephanie A. King and Nathan Johnson | Pacific Northwest National Laboratory
Lipids are a class of biomolecules that play an important role in many cellular processes. Analyses that seek to characterize all lipids in a sample—called lipidomics—are crucial to studying complex biological systems.
An important challenge in lipidomics is connecting the variety of structures of lipids with their biological functions. The positions of the double bonds within fatty acid chains is particularly important. This is because they can affect the physical properties of cellular membranes and modulate cell signaling pathways.
This information is not routinely measured in lipidomics studies because it requires a complicated experimental setup that produces complex data. Thus, scientists at Pacific Northwest National Laboratory (PNNL) developed a streamlined workflow to determine the positions of double bonds. This workflow uses both automation and machine learning approaches.
Their new method, LipidOz, streamlines the data analysis to determine the positions of double bonds. By addressing this key part of the analysis of lipids, LipidOz offers researchers a more efficient and accurate method for lipid characterization. The study is published in the journal Communications Chemistry.
The unambiguous identification of lipids is complicated by the presence of molecular parts that have the same chemical formula but different physical configurations. Specifically, the differences in these molecular parts include the fatty acyl chain length, stereospecifically numbered (sn) position, and position/stereochemistry of double bonds.
Conventional analyses can determine the fatty acyl chain lengths, the number of double bonds, and—in some cases—the sn position but not the positions of carbon–carbon double bonds. The positions of these double bonds can be determined with greater confidence using a gas-phase oxidation reaction called ozone-induced dissociation (OzID), which produces characteristic fragments.
However, the analysis of the data obtained from this reaction is complex and repetitive, and there is lack of software tool support. The open-source Python tool, LipidOz, automatically determines and assigns the double bond positions of lipids using a combination of traditional automation and deep learning approaches. New research demonstrates this ability for standard lipid mixtures and complex lipid extracts, enabling practical application of OzID for future lipidomics studies.
The “ten electron rule” provides guidance for the design of single-atom alloy catalysts for targeted chemical reactions.
A collaborative team across four universities has discovered a very simple rule to design single-atom alloy catalysts for chemical reactions. The “ten electron rule” helps scientists identify promising catalysts for their experiments very rapidly. Instead of extensive trial and error experiments of computationally demanding computer simulations, catalysts’ composition can be proposed simply by looking at the periodic table.
Single-atom alloys are a class of catalysts made of two metals: a few atoms of reactive metal, called the dopant, are diluted in an inert metal (copper, silver or gold). This recent technology is extremely efficient at speeding up chemical reactions but traditional models don’t explain how they work.
The team, which worked across the University of Cambridge, University College London, the University of Oxford and the Humboldt-University of Berlin, has published their research in Nature Chemistry. The scientists made computer simulations to unravel the underlying laws that control how single-atom alloy catalysts work.
The rule showed a simple connection: chemicals bind the most strongly to single-atom alloy catalysts when the dopant is surrounded by ten electrons. This means that scientists designing experiments can now simply use the columns on the periodic table to find which catalysts will have the desired properties for their reactions.
Dr. Romain Réocreux, a postdoctoral researcher in the group of Prof. Angelos Michaelides, who led this research, says, “When you have a difficult chemical reaction, you need a catalyst with optimal properties. On the one hand, a strong-binding catalyst may poison and stop accelerating your reaction; on the other hand, a weakly-binding catalyst may just do nothing.”
“Now we can identify the optimal catalyst just by looking at a column on the periodic table. This is very powerful since the rule is simple and can speed up the discovery of new catalysts for particularly difficult chemical reactions.”
Prof. Stamatakis, Professor of Computational Inorganic Chemistry at the University of Oxford, who contributed to the research, says, “After a decade of intense research on single-atom alloys, we now have an elegant, simple but powerful theoretical framework that explains binding energy trends and enables us to make predictions about catalytic activity.”
Using this rule, the team proposed a promising catalyst for an electrochemical version of the Haber-Bosch process, a key reaction for the synthesis of fertilizers that has been using the same catalyst since it was first discovered in 1909.
Dr. Julia Schumann, who started the project at the University of Cambridge and is now at Humboldt-Universität of Berlin, explains, “Many catalysts used in the chemical industry today were discovered in the laboratory using trial and error methods. With a better understanding of the materials’ properties, we can propose new catalysts with improved energy efficiency and reduced CO2 emissions for industrial processes.”
The migration of hydrogen in a pure magnesium layer was studied with electron spectroscopy in the ultra-high vacuum chamber in Dübendorf. Credit: Empa / AB / IFJ PAN
It is easy to be optimistic about hydrogen as an ideal fuel. It is much more difficult to come up with a solution to an absolutely fundamental problem: How to store this fuel efficiently? A Swiss-Polish team of experimental and theoretical physicists has found the answer to the question of why previous attempts to use the promising magnesium hydride for this purpose have proved unsatisfactory, and why they may succeed in the future.
Hydrogen has long been seen as the energy carrier of the future. However, before it becomes a reality in the energy sector, efficient methods of storing it must be developed. Materials—selected in such a way that at low energy cost, hydrogen can first be injected into them and then recovered on demand, preferably under conditions similar to those typical of our everyday environment—appear to be the optimal solution.
A promising candidate for hydrogen storage appears to be magnesium. Converting it into magnesium hydride, however, requires a suitably efficient catalyst, which has not yet been found.
The work of a team of scientists from Empa—the Swiss Federal Laboratories for Materials Science and Technology in Dübendorf, and the Department of Chemistry at the University of Zurich as well as the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow, has shown that the reason for the many years of failure up to this point lies in an incomplete understanding of the phenomena occurring in magnesium during hydrogen injection.
The main obstacle to the uptake of hydrogen as an energy source is the difficulty of storing it. In still-rare hydrogen-powered cars, it is stored compressed at a pressure of around 700 atmospheres. This is neither the cheapest nor the safest method, and it has little to do with efficiency: There is only 45 kg of hydrogen in one cubic meter. The same volume can hold 70 kg of hydrogen, if it is condensed beforehand.
Unfortunately, the liquefaction process requires large amounts of energy, and the extremely low temperature, at around 20 Kelvin, must then be maintained throughout storage. An alternative could be suitable materials; for example, magnesium hydride, which can hold up to 106 kg of hydrogen in a cubic meter.
Magnesium hydride is among the simplest of the materials tested for hydrogen storage capacity. Its content can reach 7.6% (by weight). Magnesium hydride devices are therefore quite heavy and so mainly suitable for stationary applications. However, it is important to note that magnesium hydride is a very safe substance and can be stored without risk; for example, in a basement, and magnesium itself is a readily available and cheap metal.
“Research on the incorporation of hydrogen into magnesium has been going on for decades, yet it has not resulted in solutions that can count on wider use,” says Prof. Zbigniew Lodziana (IFJ PAN), a theoretical physicist who has co-authored an article in Advanced Science, where the latest discovery is presented.
“One source of problems is hydrogen itself. This element can effectively penetrate the crystal structure of magnesium, but only when it is present in the form of single atoms. To obtain it from typical molecular hydrogen, a catalyst efficient enough to make the process of hydrogen migration in the material fast and energetically viable is required. So everyone has been looking for a catalyst that meets the above conditions, unfortunately without much success. Today, we finally know why these attempts were doomed to failure.”
Prof. Lodziana has developed a new model of the thermodynamic and electron processes occurring in magnesium in contact with hydrogen atoms. The model predicts that during the migration of hydrogen atoms, local, thermodynamically stable magnesium hydride clusters are formed in the material. At the boundaries between the metallic magnesium and its hydride, changes in the electronic structure of the material then occur, and it is these that have a significant role in reducing the mobility of hydrogen ions.
In other words, the kinetics of magnesium hydride formation is primarily determined by phenomena at its interface with magnesium. This effect had so far not been taken into account in the search for efficient catalysts.
Prof. Lodziana’s theoretical work complements experiments performed in the Swiss laboratory in Dübendorf. Here, the migration of atomic hydrogen in a layer of pure magnesium sputtered onto palladium was studied in an ultra-high vacuum chamber. The measuring apparatus was capable of recording changes in the state of several outer atomic layers of the sample under study, caused by the formation of a new chemical compound and the associated transformations of the material’s electronic structure. The model proposed by the researchers from the IFJ PAN allows us to fully understand the experimental results.
The achievements of the Swiss-Polish group of physicists not only pave the way for a new search for an optimal catalyst for magnesium hydride, but also explain why some of the previously found catalysts showed higher efficiency than expected.
“There is much to suggest that the lack of significant progress in hydrogen storage in magnesium and its compounds was simply due to our incomplete understanding of the processes involved in hydrogen transport in these materials. For decades, we have all been looking for better catalysts, only not where we should be looking. Now, new theoretical and experimental results make it possible to think again with optimism about further improvements in methods of introducing hydrogen into magnesium,” concludes Prof. Lodziana.
More information: Selim Kazaz et al, Why Hydrogen Dissociation Catalysts do not Work for Hydrogenation of Magnesium, Advanced Science (2023). DOI: 10.1002/advs.202304603
RoboChem is an autonomous benchtop platform for fast, accurate and around-the-clock chemical synthesis. Credit: University of Amsterdam
Chemists of the University of Amsterdam (UvA) have developed an autonomous chemical synthesis robot with an integrated AI-driven machine learning unit. Dubbed “RoboChem,” the benchtop device can outperform a human chemist in terms of speed and accuracy while also displaying a high level of ingenuity.
As the first of its kind, it could significantly accelerate chemical discovery of molecules for pharmaceutical and many other applications. RoboChem’s first results are published in the journal Science.
RoboChem was developed by the group of Prof. Timothy Noël at the UvA’s Van ‘t Hoff Institute for Molecular Sciences. Their paper shows that RoboChem is a precise and reliable chemist that can perform a variety of reactions while producing minimal amounts of waste.
Working autonomously around the clock, the system delivers results quickly and tirelessly. Noël said, “In a week, we can optimize the synthesis of about ten to twenty molecules. This would take a Ph.D. student several months.” The robot not only yields the best reaction conditions, but also provides the settings for scale-up.
“This means we can produce quantities that are directly relevant for suppliers to the pharmaceutical industry, for example.”
Time lapse of RoboChem. Credit: University of Amsterdam
RoboChem’s ‘brain’
The expertise of the Noël group is in “flow chemistry,” a novel way of performing chemistry where a system of small, flexible tubes replaces beakers, flasks and other traditional chemistry tools.
In RoboChem, a robotic needle carefully collects starting materials and mixes these together in small volumes of just over half a milliliter. These then flow through the tubing system towards the reactor. There, the light from powerful LEDs triggers the molecular conversion by activating a photocatalyst included in the reaction mixture.
The flow then continues towards an automated NMR spectrometer that identifies the transformed molecules. These data are fed back in real time to the computer that controls RoboChem.
“This is the brain behind RoboChem,” says Noël. “It processes the information using artificial intelligence. We use a machine learning algorithm that autonomously determines which reactions to perform. It always aims for the optimal outcome and constantly refines its understanding of the chemistry.”
Impressive ingenuity
The group put a lot of effort into substantiating RoboChem’s results. All of the molecules now included in the Science paper were isolated and checked manually. Noël says the system has impressed him with its ingenuity.
“I have been working on photocatalysis for more than a decade now. Still, RoboChem has shown results that I would not have been able to predict. For instance, it has identified reactions that require only very little light. At times I had to scratch my head to fathom what it had done. You then wonder: would we have done it the same way? In retrospect, you see RoboChem’s logic. But I doubt if we would have obtained the same results ourselves. Or not as quickly, at least.”
The researchers also used RoboChem to replicate previous research published in four randomly selected papers. They then determined whether Robochem produced the same—or better—results.
“In about 80% of the cases, the system produced better yields. For the other 20%, the results were similar,” Noël says. “This leaves me with no doubt that an AI-assisted approach will be beneficial to chemical discovery in the broadest possible sense.”
RoboChem is based on the principles of Flow Chemistry. Reactions are carried out in volumes of just 650 microliter, flowing through small tubes. Credit: University of Amsterdam
Breakthroughs in chemistry using AI
According to Noël, the relevance of RoboChem and other “computerized” chemistry also lies in the generation of high-quality data, which will benefit the future use of AI.
“In traditional chemical discovery only a few molecules are thoroughly researched. Results are then extrapolated to seemingly similar molecules. RoboChem produces a complete and comprehensive dataset where all relevant parameters are obtained for each individual molecule. That provides much more insight.”
Another feature is that the system also records “negative” data. In current scientific practice, most published data only reflects successful experiments. “A failed experiment also provides relevant data,” says Noël.
“But this can only be found in the researchers’ handwritten lab notes. These are not published and thus unavailable for AI-powered chemistry. RoboChem will change that, too. I have no doubt that if you want to make breakthroughs in chemistry with AI, you will need these kinds of robots.”
Credit: Journal of the American Chemical Society (2023). DOI: 10.1021/jacs.3c09195
A University of Massachusetts Amherst team has made a major advance toward modeling and understanding how intrinsically disordered proteins (IDPs) undergo spontaneous phase separation, an important mechanism of subcellular organization that underlies numerous biological functions and human diseases.
IDPs play crucial roles in cancer, neurodegenerative disorders and infectious diseases. They make up about one-third of proteins that human bodies produce, and two-thirds of cancer-associated proteins contain large, disordered segments or domains. Identifying the hidden features crucial to the functioning and self-assembly of IDPs will help researchers understand what goes awry with these features when diseases occur.
In a paper published in the Journal of the American Chemical Society, senior author Jianhan Chen, professor of chemistry, describes a novel way to simulate phase separations mediated by IDPs, an important process that has been difficult to study and describe.
“Phase separation is a really well-known phenomenon in polymer physics, but what people did not know until about 15 years ago was that this is also a really common phenomenon in biology,” Chen explains. “You can look at phase separation with a microscope, but to understand this phenomenon at the molecular level is very difficult.
“In the past five or 10 years, people have started to discover that many of these disordered proteins can drive phase separation, including numerous important ones involved in cancer and neurodegenerative disorders.”
The new paper, based on research in Chen’s computational biophysics and biomaterials lab, constitutes one chapter of lead author Yumeng Zhang’s Ph.D. dissertation. Zhang will start work as a postdoctoral researcher at Massachusetts Institute of Technology (MIT) in February. Another key contributor is Shanlong Li, a postdoctoral research associate in Chen’s lab.
Chen’s lab developed an accurate, GPU-accelerated hybrid resolution (HyRes) force field for simulating phase separations mediated by IDPs. This model is unique in its ability to accurately describe peptide backbone interactions and transient secondary structures, while being computationally efficient enough to model liquid-liquid phase separation. This new model fills a critical gap in the existing capability in computer simulation of IDP phase separation.
Chen and team created HyRes simulations to demonstrate for the first time what governs the condensate stability of two important IDPs.
“I actually did not anticipate that it could do such a good job at describing phase separation because it’s a really difficult phenomenon to simulate,” Chen says. “We demonstrated that this model is accurate enough to start looking at the impacts of even a single mutation or residual structures in the phase separation.”
The researchers’ HyRes-GPU provides an innovative simulation tool for studying the molecular mechanisms of phase separation. The ultimate goal is to develop therapeutic strategies in the treatment of diseases associated with disordered proteins.
“This is really the significance of this work,” Chen says. “Important biological processes are believed to occur through phase separation. So, if we can understand better what controls this process, that knowledge will be really powerful, if not essential, for us to think about controlling phase separation for various scientific and engineering purposes. This will help us understand the type of intervention that will be required to achieve therapeutic effects.”
Chen says the next step is to apply what his team has learned to larger-scale simulations of more complex biomolecular mixtures.
“Shanlong is now working on constructing a similar model for nucleic acids because phase separation often involves both disordered proteins and nucleic acids,” he says. “We want to be able to describe both key components, and that would allow us to look at many more systems.”
More information: Yumeng Zhang et al, Toward Accurate Simulation of Coupling between Protein Secondary Structure and Phase Separation, Journal of the American Chemical Society (2023). DOI: 10.1021/jacs.3c09195
The hydrogel fibers printed on the glass are covered by partially crosslinked dangling chains, exhibiting great affinity toward water molecules. They act like the grooves on the integuments of lizards to collect droplets and their surface could form a hydration layer to mimic the mucus on the catfish skin to make droplet movement more smooth and quick. Credit: Science China Press
The water in the air originates from both natural and forced evaporation, with condensation being the final and crucial step in water harvesting. Condensation involves nucleation, growth, and shedding of water droplets, which are then collected.
However, uncontrollable growth of condensed droplets leading to surface flooding is a pressing challenge due to insufficient driving forces, posing a threat to sustainable condensation.
A study, led by Prof. Jiuhui Qu, Dr. Qinghua Ji, and Dr. Wei Zhang from Tsinghua University, focuses on addressing water scarcity by exploring atmospheric water harvesting. The work is published in the journal National Science Review.
To expedite this process and achieve orderly and rapid droplet shedding from the condensing surface, the team took inspiration from nature. They observed that the Australian thorny devil efficiently spread droplets, such as rains, dews, and pond water, from its scales to capillary channels between the scales, eventually connecting to its mouth.
This natural mechanism made water easier to store and consume. Additionally, the team drew inspiration from fish, particularly catfish, which possess an epidermal mucus layer reducing swimming drag and enhancing adaptability to aqueous environments. These insights from nature address the challenges of orderly droplet navigation and low-drag droplet shedding, respectively.
The research team employed hydrogel fibers to create an engineered pattern on glass, incorporating the advantageous features of both lizards and catfish.
The hydrogel fiber is an interpenetrated network of sodium alginate and polyvinyl alcohol with a partially polymerized surface and arch structure. The surface, adorned with branched –OH and –COOH chains, exhibits a strong affinity for water molecules.
This affinity, coupled with the arch structure, provides sufficient driving force for droplets to move from the condensing substrate to the hydrogel fiber. Simultaneously, the branched –OH and –COOH chains can retain water molecules even after droplets leave the surface, aiding in the formation of a precursor water film that lubricates droplet sliding.
The fluorescent molecules were first immobilized on the glass as probes. After condensation, droplets re-dissolved the probes and quickly transferred from the glass to the hydrogel fiber and then slid along the fiber quickly. Credit: Science China Press
To observe droplet movement, fluorescent molecules were utilized as probes. The captured trajectories revealed an impressive migration rate, with droplets formed on the glass swiftly pumped to the hydrogel fiber, thereby regenerating the condensing sites.
The success lies in the concurrent application of chemical wetting gradients and the Laplace pressure difference across the hydrogel fiber and the glass. The pumping effect resulted in a reduction of over 40% in the energy of the droplet-condensing surface system, acting as the driving force source. “This is similar to the directional water dispersion over the integuments of lizards,” Professor Qu notes.
The researchers also observed distinctions in the movement of water on the hydrogel fiber surface compared to that on glass. On the glass, droplets advanced as a cohesive unit with successive formation of new advancing angles, resulting in complete mixing of fluorescent probes within the droplet during advancement.
In contrast, droplet sliding on the hydrogel fiber surface exhibited a layered behavior. The inner layer of water bonded to the hydrogel surface, while the outer layer slid without direct contact with the hydrogel surface.
“The dangling chains over the hydrogel surface act like the mucus layer of the catfish, lubricating the friction between the droplets and the condensing surface,” explains Dr. Ji.
This engineered hydrogel fiber pattern increased the condensation rate by 85.9% without requiring external energy input. Moreover, it was successfully applied to enhance the water collection rate of solar evaporative water purification by 109%.
This study not only provides insights into natural phenomena but also marks a novel attempt to manipulate droplet movement for condensation. The findings lay the foundation for future endeavors in discovering phenomena and translating theories into practical applications.
More information: Wei Zhang et al, Pumping and sliding of droplets steered by a hydrogel pattern for atmospheric water harvesting, National Science Review (2023). DOI: 10.1093/nsr/nwad334
