Category: Chemistry

by Chinese Academy of Sciences

NH₃ is the second largest chemical produced in the world and nearly 80% of produced NH₃ is employed in fertilizer synthesis. Meanwhile, NH₃ is an indispensable raw material for manufacturing nitric acid, which can be further employed in chemical production.

Moreover, NH₃ possesses high hydrogen capacity, making it a potential carbon-free fuel. As one of the greatest inventions, the Haber-Bosch process enables the large-scale production of value-added NH₃; however, it is against the principle of sustainable development theory due to the high operational costs and negative environmental impacts of the Haber-Bosch process.

Hence, it is imperative to explore green and sustainable approaches to produce NH₃ and simultaneously realize global environmental sustainability.

Artificial electrocatalytic NH₃ synthesis (which can couple with clean renewable electricity) is recently becoming a research hotspot, where the majority of researchers use N₂ gas as the N source. Although electrocatalytic N₂ reduction reaction (NRR) provides an eco-friendly and sustainable route for ambient NH₃ production, the conversion efficiency of N₂ reduction to NH₃ is unsatisfactory because of the high thermodynamic stability of the N₂ molecule.

Fortunately, the more active N sources (i.e., NO, NO₂⁻, NO₃⁻) have been deemed as attractive precursors to achieve effective NH₃ production, and meanwhile, the development of electrocatalytic NO reduction reaction (NORR) and NO₃⁻/NO₂⁻ (NO_x⁻) reduction reaction (NtrRR) is also expected to control and mitigate the related environmental pollution.

Although many promising studies have been done in the field of artificial electrosynthesis of NH₃, the design and development of active electrocatalysts with high selectivity and stability to achieve efficient NH₃ production remain certain challenges.

Recently, a research team led by Prof. Xuping Sun from University of Electronic Science and Technology of China introduced three electrochemical NH₃ synthesis routes (NRR, NORR, and NtrRR) then summarized recent advances in electrocatalyst development for ambient NH₃ synthesis, mainly involving catalytic mechanisms, theoretical advances, and electrochemical performance.

The challenges and future perspectives are also proposed in the concluding remarks, aiming to provide experience and inspire more critical insights for the electrocatalytic NH₃ synthesis reactions. The results were published in the Chinese Journal of Catalysis.

More information: Ling Ouyang et al, Recent advances in electrocatalytic ammonia synthesis, Chinese Journal of Catalysis (2023). DOI: 10.1016/S1872-2067(23)64464-X

Provided by Chinese Academy of Sciences 

by Tampere University

Joint research groups at Tampere University, University of Helsinki, Lund University and Pi-Numerics, Salzburg, have established key early steps in the conversion of aromatic molecules, a major constituent of traffic and other urban volatile emissions, into aerosol. Published in Nature Communications, their findings increase understanding of the chemical processes that degrade urban air quality and influence climate change.

Many aromatic molecules are carcinogenic and have negative impacts on health. Their primary source is exhaust fumes from motor vehicles. Aromatics can form aerosol particles when they collide in the atmosphere with the hydroxyl radical, a molecule colloquially dubbed “atmospheric detergent” due to its acute propensity to react chemically.

When breathed in, aerosol particles can lead to a myriad of chronic health issues and even death. These particles also affect Earth’s climate by reflecting sun light and increasing the formation of clouds.

Despite their importance to the urban environment, details of the reaction processes that form aerosol from aromatics have until now remained unresolved.

The group of researchers used a combination of quantum mechanics, targeted experiments, and modeling to establish the early steps in the reaction process of toluene, one of the most abundant aromatic molecules.

“We found out that a reaction product that was previously thought to be stable is in fact transient and converts to new hot molecules. These molecules have residual energy that makes subsequent chemistry fast and promptly lead to aerosol precursor products,” says Siddharth Iyer, Postdoctoral Research Fellow of Aerosol Physics at Tampere University.

“This result bridges the gap between theory and observation and provides better understanding of the chemistry of aerosol formation in urban environments.”

More information: Siddharth Iyer et al, Molecular rearrangement of bicyclic peroxy radicals is a key route to aerosol from aromatics, Nature Communications (2023). DOI: 10.1038/s41467-023-40675-2

Journal information: Nature Communications 

Provided by Tampere University

by Universität Paderborn

Scientists from Paderborn University, working under Professor Matthias Bauer, have achieved a breakthrough in the field of sustainable chemistry: together with a team of researchers from the universities of Rostock, Mainz, Göttingen, Innsbruck and Kassel, they have developed a chemical complex that converts light into energy for reactions and optical applications—in a sustainable way, since the material can be used to save huge amounts of CO₂.

The new compound has potential applications in areas such as diodes, or in converting solar energy into chemical energy. The results have now been published in Nature Chemistry.

Saving carbon dioxide

“What makes this complex special is that unlike the systems currently in use, it contains iron as the central element,” Bauer explains. Previously, precious-metal-based compounds were generally used for photochemical reactions and photophysical applications.

“However, manufacturing these produces carbon dioxide emissions of around 30 tons per kilogram. If precious metals are replaced with iron, the potential reduction in climate-damaging CO₂ is huge,” Bauer adds. By comparison, manufacturing a kilogram of iron only produces around two kilograms of the climate-damaging gas.

‘Sustainability to the power of two’

“For the first time, the design of the compound being examined has enabled us to implement a property that is extremely rare in chemical compounds and unprecedented in iron compounds,” explains Dr. Jakob Steube, one of the key members of Bauer’s team. The complex glows in two different colors when exposed to light of a certain energy.

These photophysical properties will for example enable white light-emitting diodes to be made using iron compounds. In addition, the complex can be used to transform solar energy into chemical energy.

“We were able to demonstrate that following absorption with light, chemical reactions are possible with our new compound,” Bauer explains. “This gives us sustainability to the power of two, namely energy conversion using a virtually CO₂-neutral compound plus the combination of areas of application in photochemistry and photophysics. This can absolutely be described as a mini breakthrough.”

These findings were gained as part of the priority program “Light-controlled reactivity of metal complexes.” Headed by co-author Professor Katja Heinze of the University of Mainz, the program examines the question of how to ensure sustainable chemical reactions in the future despite increasingly scarce resources, as well as ways of using new energy sources such as sunlight.

More information: Jakob Steube et al, Janus-type emission from a cyclometalated iron(iii) complex, Nature Chemistry (2023). DOI: 10.1038/s41557-023-01137-w

Journal information: Nature Chemistry 

Provided by Universität Paderborn

by Chiba University

Lanthanide-containing complexes are important compounds for sophisticated nuclear-fuel processing and medical imaging. Moreover, they often have interesting symmetric crystal structures and associated dynamics that render unique properties for practical applications. The seven-coordinate lanthanide complex Ho(III) aqua-tris(dibenzoylmethane) or Ho-(DBM)₃·H₂O was first reported in the late 1960s.

It has a three-fold symmetric structure with holmium (Ho) at the center of three propeller-shaped dibenzoylmethane (DBM) ligands and a water (H₂O) molecule hydrogen-bonded to the ligands. Unfortunately, the understanding of the molecular dynamics (MD) of such lanthanide complexes has been limited due to challenges in describing their interactions using the classical MD framework.

This motivated a team of researchers from the Graduate School of Engineering at Chiba University, led by Associate Professor Takahiro Ohkubo, to elucidate the structure and dynamics of the Ho-(DBM)₃·H₂O complex. This study was published in Inorganic Chemistry and is co-authored by Associate Professor Hyuma Masu, Professor Keiki Kishikawa, and Associate Professor Michinari Kohri.

“Hydrogen bonds between the water molecule and the ligands surrounding Ho are considered to play an important role in the formation of the symmetrical structure of the novel lanthanide complex. After synthesizing its single crystal and bulk samples, the next logical step was to model this complex to test this hypothesis and understand its structure and dynamics,” explains Dr. Ohkubo.

Considering the shortcomings of existing general force-fields (a functional form used to estimate forces between atoms) in satisfactorily describing the interactions of lanthanide metals such as Ho, the researchers developed new force-field parameters for conducting classical MD simulations of the Ho-(DBM)₃·H₂O complex. They performed structural optimization and MD steps using ab initio calculations based on the plane-wave pseudopotential method to make training data for force-fields’ development.

Further, the team tuned the force-field parameters for the simulations to reproduce the data obtained from the ab initio calculations. They validated the thus-obtained novel force-field using both the experimental crystalline structure information as well as the theoretical ab initio data. The lattice constant and atomic distances around Ho calculated using the new force-field parameters were found to be in good agreement with the observations of single-crystal X-ray diffraction.

On examining the vibrational properties of water in the Ho-(DBM)₃·H₂O complex and comparing them to those in bulk liquid water, they observed that the vibrational motion of water in the complex had a characteristic mode.

It originated from stationary rotational motion along the c-axis of Ho-(DBM)₃·H₂O. Remarkably, the hydrogen bond dynamics of water, including lifetime, in seven-coordinate lanthanide complexes are quite like those in bulk water, except for librational or reciprocating motion. This novel finding is contrary to basic expectations.

In summary, this innovative strategy of developing force-field parameters for classical MD examination unveils the role of water dynamics in complexes such as Ho-(DBM)₃·H₂O. As Dr. Ohkubo explains, “This approach helped us understand the nature of metal complexes of lanthanides with water and actinide metals with high coordination numbers. In the future, this strategy could possibly pave the way for accurate molecular simulations of any metal complex and prediction of its structure and dynamics.”

More information: Takahiro Ohkubo et al, Molecular Dynamics Studies of the Ho(III) Aqua-tris(dibenzoylmethane) Complex: Role of Water Dynamics, Inorganic Chemistry (2023). DOI: 10.1021/acs.inorgchem.3c01277

Provided by Chiba University

by Washington University in St. Louis

Chenfeng Ke, an incoming associate professor of chemistry in Arts & Sciences at Washington University in St. Louis, developed a unique design for tough but stretchable hydrogels, reported Aug. 23 in the journal Chem. The new material is both flexible and durable thanks to a ring-shaped sugar molecule that encases its polymer network and allows it to stretch without sacrificing strength.

Ke can 3D-print the so-called crystalline-domain reinforced slide-ring hydrogels, or CrysDoS-gels. He and his co-authors also created a materials library and offer methods for how the material can be added to existing materials to enhance their durability, such as in plastic additives to enhance the durability for parts in automobiles in the future.

“There are a series of tradeoffs with these traditional plastic materials—they’re usually one or the other,” stretchable or rigid, Ke said. “But if you connect two things with a slidable joint, you have very interesting properties of both.”

The new material is simple and adaptable, Ke said, and can be combined with a variety of hydrogels to improve the properties of different plastics. For example, it could be added to stretchable materials to make them stronger, or to rigid materials to make them more flexible. In this study, the chemists demonstrated a potential application of their newly discovered CrysDoS-gels by 3D-printing them as stress sensors.

“Think of it increasing the lifespan of plastic parts to reduce the waste we produce,” Ke said.

More information: Chenfeng Ke, Reinforced double-threaded slide-ring networks for accelerated hydrogel discovery and 3D printing, Chem (2023). DOI: 10.1016/j.chempr.2023.07.020. www.cell.com/chem/fulltext/S2451-9294(23)00371-6

Journal information: Chem 

Provided by Washington University in St. Louis 

by University of California, Irvine

A research team led by University of California, Irvine scientists has developed an innovative method for quickly and efficiently creating vast collections of chemical compounds used in drug discovery by harnessing the power of ribosomes, the molecules found in all cells that synthesize proteins and peptides.

Findings recently published in ACS Central Science describe this transformative technique, which could replace the current manually intensive process, accelerating the discovery of new drugs that could affect treatment of a wide array of diseases and conditions.

Chemical libraries are collections of molecules that are screened to identify those with promising activity or therapeutic potential. Screening involves asking the same biological question of each chemical in the library in the form of a rapid experiment or assay.

“Library synthesis and screening are the first steps in the discovery of new medicines,” said Brian M. Paegel, UCI professor of pharmaceutical sciences and the study’s co-corresponding author. “This new technology allows us to synthesize libraries of ultra-miniaturized gel beads that each contain hundreds of thousands of copies of a single compound from the library. The arrangement of so many copies of molecules on beads allows scientists to evaluate the biological activity of each library member directly, an invaluable capability in the search for new medicines.”

The team invented a novel approach to generate gel beads that are roughly the size of a human cell, each containing vast quantities of ribosomes, an enzyme called RNA polymerase and a magnetic core adorned with DNA, not unlike a human cell’s nucleus. The DNA cores encode—or provide assembly instructions for—specific peptide molecules. Insulin is an example of a naturally occurring peptide that has become a drug.

By mimicking a cell’s flow of genetic information from DNA to RNA to peptide synthesis, the researchers successfully localized genetically encoded peptide synthesis within each individual gel bead. Importantly, this technique can be executed in parallel on millions of beads, each with a unique DNA tag, forming an expansive library.

“The beads themselves are also an important achievement. Chemical synthesis that currently depends on labor-intensive manual procedures is now facilitated by the ribosome, allowing us to prepare very large libraries using nature as our inspiration. Scientists can now explore a vast number of molecules simultaneously, advancing pharmaceutical discoveries, while the DNA-encoded magnetic cores enable efficient tracking and analysis of individual compounds,” said Paegel, who also has appointments in chemistry and biomedical engineering.

This method also has applications in other areas, such as enzyme engineering, the development of environmentally friendly pesticides or the creation of materials with specific physical properties.

Other team members included co-corresponding author Christian Cunningham and Alix Chan, both scientists at Genentech in South San Francisco, and Valerie Cavett, UCI project specialist in pharmaceutical sciences.

More information: Valerie Cavett et al, Hydrogel-Encapsulated Beads Enable Proximity-Driven Encoded Library Synthesis and Screening, ACS Central Science (2023). DOI: 10.1021/acscentsci.3c00316

Journal information: ACS Central Science 

Provided by University of California, Irvine 

SRCs) are inexpensive, lightweight, and have advantages in terms of disposal and recycling as the reinforcement and the base material are composed of the same material. For this reason, it is attracting attention as a next-generation composite material to replace carbon fiber-reinforced composites used in aircraft.

The Korea Institute of Science and Technology (KIST) has announced that Dr. Jaewoo Kim of the Solutions to Electromagnetic Interference in Future-mobility (SEIF), together with Prof. Seonghoon Kim of Hanyang University and Prof. O-bong Yang of Jeonbuk National University have successfully developed a 100% SRC using only one type of polypropylene (PP) polymer. Their work is published in the Chemical Engineering Journal.

Until now, in the manufacturing process of SRCs, chemically different components have been mixed in the reinforcement or matrix to improve fluidity and impregnation, resulting in poor physical properties and recyclability. The research team succeeded in controlling the melting point, fluidity, and impregnation by adjusting the chain structure of the polypropylene matrix through a four-axis extrusion process.

The developed SRCs achieved the highest level of mechanical properties, with adhesion strength, tensile strength, and impact resistance improved by 333%, 228%, and 2,700%, respectively, compared to previous studies. When applied as a frame material for a small drone, the material was 52% lighter than conventional carbon fiber reinforced composites and the flight time increased by 27%, confirming its potential for next-generation mobility applications.

Dr. Kim of KIST said, “The engineering process for 100% SRCs developed in this study can be immediately applied to industry, and we will continue to work with the joint research team and industries to secure the global competitiveness of magnetically reinforced composites.”

More information: Hyeseong Lee et al, True self-reinforced composites enabled by tuning of molecular structure for lightweight structural materials in future mobility, Chemical Engineering Journal (2023). DOI: 10.1016/j.cej.2023.142996

Provided by National Research Council of Science & Technology

In a cutting-edge discovery, published in the Journal of the American Chemical Society, Florey scientists have solved a long-standing problem: the need for an affordable, simple way to make peptide-based drugs that hold their necessary shape.

Professor Akhter Hossain, Head of the Insulin Peptides Group at The Florey, said peptides, the smaller relatives of proteins, are easy to make in a laboratory, have therapeutic potential and are considered safe. However, without the proper structure, the peptides become floppy and inactive.

“Peptides form unique structures that fit like jigsaw pieces into receptors in the brain or elsewhere in the body. They modulate a diverse range of essential bodily functions.”

Professor Hossain said our bodies naturally use complicated means of introducing structure into peptides to make them work, which is challenging to replicate in the drug development.

“Peptide stapling has been highly successful in overcoming this problem but the current methods are costly and involve complex chemistry and purification,” he said.

The paper’s lead author and Head of The Florey’s Neurotherapeutics Theme, Professor Ross Bathgate, said by simplifying peptide stapling, the team had turned a multi-step, week-long process into a shorter, single-step one.

“Our new approach is flexible, easy to implement, and will make it easier for researchers and pharmaceutical companies to develop peptide-based drugs. Now we can easily make peptides with the correct structure to bind to their target receptors. Our ultimate goal is for this technology to be used to treat a range of disorders,” Professor Bathgate said.

“In our laboratories at The Florey we’ve used this technology successfully in the earliest stage of drug discovery, and believe it will likely be applicable to a range of potential therapeutic targets for peptide-based drugs,” Professor Hossain said.

More information: Ross A. D. Bathgate et al, Noncovalent Peptide Stapling Using Alpha-Methyl-l-Phenylalanine for α-Helical Peptidomimetics, Journal of the American Chemical Society (2023). DOI: 10.1021/jacs.3c02743

Journal information: Journal of the American Chemical Society 

Provided by Florey Institute of Neuroscience and Mental Health

The ordered areas of proteins are readily studied. Consequently, a great deal is known about the role of these areas in the biological function of the respective proteins. However, an international research team led by biochemist Prof. Dr. Ute Hellmich has shown that disordered areas are also pivotal.

Their comprehensive examination of the disordered area of a receptor channel protein has been published in the journal Nature Communications. The group demonstrated through eleven different methods how this area influences the function of the entire protein. Therefore, disordered protein areas should not be overlooked in research, even though they may not always be straightforward to investigate.

Investigating disorder in proteins

Proteins play a part in all processes of life. They facilitate the reading and duplication of genetic material, digest nutrients and carry out countless other essential functions. These large protein molecules can be best researched when they have a clear structure—that is, when the individual areas within the molecules are ordered.

“Classically, these proteins would be examined using X-ray crystallography or cryo-electron microscopy. But these methods are most suited for regular, or ordered, structures,” explains Hellmich. “For this reason, in some studies the disordered areas are intentionally removed to better examine the remaining molecule. But if you are specifically interested in that area, that is of course not an option.”

Hellmich and her team specifically studied a very large, disordered area of the receptor channel protein TRPV4. “So-called Transient Receptor Potential Channels, which include TRPV4, control our perception of pain and temperature and play a crucial role in the immune system and during infections,” Hellmich elucidates her research subject. “There are more than 60 known mutants of TRPV4 that cause serious illnesses. This clearly indicates how significant these proteins are,” she adds.

“In some representatives of this protein class, the disordered area comprises half of the entire molecule. This alone demonstrates that these domains cannot be overlooked,” continues the biochemist. The TRPV4 protein that her team studied has one of the largest disordered areas of this protein class in mammals, specifically containing about 130 to 150 individual amino acids. If you cut off this disordered area, TRPV4 loses its function.

A multidisciplinary perspective

In their work, the researchers used a total of eleven different biochemical and biophysical methods in various combinations—from nuclear magnetic resonance spectroscopy to mass spectrometry to molecular dynamic simulations. “At some points, we pursued a research question with different methods at the same time. We simply wanted to be quite certain that we understand the receptor correctly,” explains Hellmich. “This approach enabled us to create a molecular map of this disordered area. Thus, we discovered a network of various activity-determining elements that activate or deactivate the receptor depending on the chemical environment.

“When you consider that these disordered areas of receptor channel proteins have not been viewed in this way before, our research work certainly opens a completely new perspective on protein research and the biological function and regulation of receptors by their disordered areas,” Hellmich says. “Whether it might even be a paradigm shift, we will likely see in the coming years. I am confident that our further work within the framework of the ‘Balance of the Microverse’ excellence cluster here at the university will contribute to this,” says the scientist.

More information: Benedikt Goretzki et al, Crosstalk between regulatory elements in disordered TRPV4 N-terminus modulates lipid-dependent channel activity, Nature Communications (2023). DOI: 10.1038/s41467-023-39808-4

Journal information: Nature Communications 

Provided by Friedrich-Schiller-Universität Jena

Chitin hydrogel is recognized as a promising material for a variety of biomedical applications. Its biocompatibility and biodegradability make it useful in tissue repair, artificial organs, and wound healing. Yet scientists continue to face challenges in fabricating chitin hydrogel. A team of researchers has developed a green, efficient and scalable preparation method for chitin hydrogels.

The team’s work provides a rational strategy to fabricate chitin hydrogels and paves the way for its practical applications as a superior biomedical material.

Their findings are published in the journal Nano Research.

Chitin, the second most abundant natural polymer, is a substance that comes from the exoskeletons of crabs, prawns, and insects. Chitin is renewable, degradable, biocompatible and low-cost. These qualities make it an excellent candidate for various biomedical uses.

“Chitin hydrogel, which shares many similarities with extracellular matrix, is an ideal material for tissue engineering and regenerative medicine. However, it is a challenge to dissolve chitin in aqueous solutions to produce hydrogel materials. Therefore, it is of great significance to develop rational fabrication strategy,” said Li-Bo Mao, a professor at the University of Science and Technology of China.

To be useful in biomedical applications, the chitin hydrogel must be biologically safe and have the appropriate mechanical strength and chemical stability. It must resist biofouling, which could lead to inflammatory response or immune rejection in the human body. For commercial use, the chitin hydrogel must also be low-cost and scalable.

The challenges in fabricating strong chitin hydrogel arise because of the insolubility of chitin in many solvents and the reduced chain length of chitin regenerated from solutions. Biopolymer hydrogels are typically prepared with a two-step process: the dissolution of the biopolymer and the subsequent gelation.

However, chitin is not soluble in water or other common solvents because of the numerous inter- and intra-molecular hydrogen bonds between the polymer chains. The team tackled this challenge by fabricating chitin hydrogel with biomimetic structure through the chemical transformation of chitosan, a water-soluble deacetylated derivative of chitin.

Chitosan is easily dissolved in water in the presence of acids. These chitosan hydrogels can be endowed with different microstructures. However, they are not mechanically or chemically stable. Attempts to improve them by using crosslinking agents have raised biosafety concerns.

The team was successful in fabricating a chemically stable and antifouling chitin hydrogel via a chemical reaction called acetylation. Through the acetylation process, the chitin hydrogel the team obtained possesses outstanding resistance to swelling, degradation, extreme temperature and pH conditions, and organic solvents.

The team also learned that by templating the chitosan precursor with ice crystals, they could produce chitin hydrogels with different biomimetic structures. These structures can be either nacre-like or wood-like depending on the freezing method used with the chitosan precursor.

The chitin hydrogel developed by the team has excellent mechanical properties while retaining a high water content. It also shows excellent antifouling performance, resisting the adhesion of proteins, bacteria, blood, and cells.

“Besides the many advantages that are characteristic to chitin, the hydrogel materials we obtained are mechanically strong and robust. In addition, the hydrogels can be feasibly processed into different shapes and structures. These ensure the practical applications of the chitin hydrogels,” said Mao.

Looking ahead, the team’s next step is to further improve the mechanical properties of chitin hydrogels and explore their biomedical applications via in vivo experiments. “We anticipate various chitin-based hydrogel materials can be fabricated through this strategy and used for different clinical applications, such as cartilage replacement, bone replacement, wound dressing and even artificial organs,” said Mao.

More information: Rui-Rui Liu et al, Biomimetic chitin hydrogel via chemical transformation, Nano Research (2023). DOI: 10.1007/s12274-023-5886-5

Journal information: Nano Research 

Provided by Tsinghua University Press