Category: Chemistry

Glycolipids, basically “fatty sweet” molecules, are a relatively unknown group of lipids. A new method developed by an Austrian team led by chemist Evelyn Rampler of the University of Vienna has now provided deeper insights into the functioning of certain glycolipids located on the surfaces of stem cells. The approach presented by the researchers from the University of Vienna, BOKU Vienna and the University of Graz in the open access Journal of the American Chemical Society Au can be applied to a wide range of glycolipid classes.

Pioneering developments in glycoscience for determining the function of sugar structures on cell surfaces recently received recognition with the Nobel Prize in Chemistry awarded to Carolyn Bertozzi. However, research into the class of fatty sweet molecules known as glycolipids is a relatively new, emerging field of study. With their recent work, chemist Evelyn Rampler of the University of Vienna and her colleagues are providing important basic research for this area. Using highly sensitive tools such as mass spectrometry, the structural properties of glycolipids can be investigated.

Decoding of gangliosides

This study aimed at developing a measurement and data analysis method for a specific class of relatively unknown glycolipids, so-called gangliosides, whose composition changes on the cell membrane during stem cell differentiation.

“Previous approaches have not been able to determine the multiple functions of gangliosides in Alzheimer’s disease, dementia or cancer because they lacked the necessary sensitivity. With our new method, we now provide a tool for the comprehensive analysis of gangliosides,” says Evelyn Rampler, group leader at the Institute of Analytical Chemistry at the University of Vienna.

A research consortium of the Medical University Vienna and the University of Vienna will now investigate the relevance of gangliosides and other fatty sweet molecules in cancer. To monitor sugar structures on cells in even greater detail, it would be also possible to combine this new method with the bioorthogonal labeling introduced by Nobel Prize winner Carolyn Bertozzi.

Study of human stem cells

“Our study on human stem cells has shown that the existing patterns of gangliosides change massively depending on which cells or tissues develop from the stem cells. It was therefore possible to identify new markers for different cell types, which now have to be confirmed in independent studies including larger sample sizes,” says Evelyn Rampler.

“Based on our new mass spectrometry method, we were able to measure and describe the molecular diversity of gangliosides in an unprecedented level of detail,” says first author and chemist Katharina Hohenwallner from the University of Vienna.

The study involved experiments with stem cells, carried out by Dominik Egger of the Institute of Cell and Tissue Culture Technologies at BOKU Vienna. In addition, the software “Lipid Data Analyzer” for gangliosides was adapted together with researchers from the University of Graz, Institute of Pharmaceutical Sciences.

Surgical tissue waste as samples

For the analysis, the team used tissue samples derived from medical waste. First, the so-called mesenchymal stem cells were isolated from the tissue and allowed to differentiate into bone, cartilage, and fat cells. In the course of the study, the largest number of gangliosides were identified to date.

Additionally, gangliosides were identified as potential markers to distinguish the different cell types at the chemical level. Based on automated data analysis, the researchers provide a method to comprehensively measure and structurally describe the gangliosides for the first time.

To guide the design and synthesis of electrocatalysts toward highly efficient oxygen evolution reactions (OER), researchers from the Beijing University of Chemical Technology have summarized four common strategies to improve the OER performance of layered double hydroxides (LDHs) as well as identifying active sites for LDHs.

They published their work on Sep. 7 in Energy Material Advances.

“With the rising demand and consumption of fossil fuels, energy shortage and environmental pollution are becoming severe and unignorable,” said the corresponding author Mingfei Shao, professor with the State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing. “It is necessary to explore sustainable and renewable energy. Hydrogen, especially, is a new energy with splendid application prospects.”

Production of highly pure hydrogen can be achieved by electrochemical water splitting using the electricity transformed from renewable energies such as wind and solar. But as one of the half reactions, OER is a four-electron process, with a low-efficiency energy utilization, according to Shao.

Shao and his team focus on LDHs, a large type two-dimensional material. The wide tunability, molar ratios and interlayer anions, make it an outstanding catalysts for OER in alkaline medias.

“We summarized four common strategies applied to improve the OER performance of LDHs. Through these strategies, the overpotential of OER can be decreased, leading to a high efficiency of energy utilization,” Shao said. “Some works about the identification of active sites for LDHs are introduced. Revelation of reaction mechanism and active sites provide the theoretical guidance to design efficient electrocatalysts.”

The development and exploration of OER catalysts is mostly in the experimental stage at present, which cannot meet the standards for large-scale practical use. For instance, problems related to enlarging the size of the catalysts and maintaining stability during OER remain. Additionally, most reported preparation methods of LDH-based catalysts are complicated and time-consuming, which results in high costs and restricts their application, according to Shao.

“The recognition of reactive oxygen species such as oxygen species adsorbed by active sites on the surface of electrocatalysts and oxygen radical dispersed in the solution during OER still remains ambiguous due to the instable and unapparent existence of reactive oxygen species,” Shao said. “After recognizing these reactive oxygen species, how to take advantage of them for more efficient OER is still vital.”

“We hope this review can offer ideas to further identify the active sites for LDHs with the purpose of providing guidance to design more advanced electrocatalysts towards electrochemical water splitting,” Shao said.

A research team affiliated with UNIST recently reported that the performance of electrodes for an alkaline hydrogen evolution reaction (HER) can be significantly improved even without expensive electrocatalysts and complicated processes by modifying them with superaerophobic polymeric hydrogels. This breakthrough has been led by Professor Jungki Ryu and his research team in the Department of Energy Engineering at UNIST.

In this study, the research team reported a simple strategy to enhance the efficiency of electrochemical hydrogen production by imparting superaerophobicity to an underlying electrode with porous polymeric hydrogels. Superaerophobic hydrogels were readily coated on target substrates by cross-linking polyethyleneimine (PEI) via Schiff-base condensation reactions followed by freeze-drying, noted the research team.

As a result, they could readily control the pore size, porosity, and superaerophobicity of the hydrogel-coated electrodes by varying the concentrations of PEI upon cross-linking. Due to facile removal of as-generated hydrogen bubbles, the NF electrode modified with PEI hydrogel only outperformed those modified with expensive electrocatalysts especially at high current densities, according to the research team.

“We believe that our results can pave the way for the practical application of water electrolysis by providing insights into the design of electrodes and electrolyzers,” noted the research team.

This study has been published in Advanced Energy Materials.

Researchers have discovered a potential new method for making the high-performance magnets used in wind turbines and electric cars without the need for rare earth elements, which are almost exclusively sourced in China.

A team from the University of Cambridge, working with colleagues from Austria, found a new way to make a possible replacement for rare-earth magnets: tetrataenite, a “cosmic magnet” that takes millions of years to develop naturally in meteorites.

Previous attempts to make tetrataenite in the laboratory have relied on impractical, extreme methods. But the addition of a common element—phosphorus—could mean that it’s possible to make tetrataenite artificially and at scale, without any specialized treatment or expensive techniques.

The results are reported in the journal Advanced Science. A patent application on the technology has been filed by Cambridge Enterprise, the University’s commercialization arm, and the Austrian Academy of Sciences.

High-performance magnets are a vital technology for building a zero-carbon economy, and the best permanent magnets currently available contain rare earth elements. Despite their name, rare earths are plentiful in Earth’s crust. However, China has a near monopoly on global production: in 2017, 81% of rare earths worldwide were sourced from China. Other countries, such as Australia, also mine these elements, but as geopolitical tensions with China increase, there are concerns that rare earth supply could be at risk.

“Rare earth deposits exist elsewhere, but the mining operations are highly disruptive: you have to extract a huge amount of material to get a small volume of rare earths,” said Professor Lindsay Greer from Cambridge’s Department of Materials Science & Metallurgy, who led the research. “Between the environmental impacts, and the heavy reliance on China, there’s been an urgent search for alternative materials that do not require rare earths.”

Tetrataenite, an iron-nickel alloy with a particular ordered atomic structure, is one of the most promising of those alternatives. Tetrataenite forms over millions of years as a meteorite slowly cools, giving the iron and nickel atoms enough time to order themselves into a particular stacking sequence within the crystalline structure, ultimately resulting in a material with magnetic properties approaching those of rare-earth magnets.

In the 1960s, scientists were able to artificially form tetrataenite by bombarding iron-nickel alloys with neutrons, enabling the atoms to form the desired ordered stacking, but this technique is not suitable for mass production.

“Since then, scientists have been fascinated with getting that ordered structure, but it’s always felt like something that was very far away,” said Greer. Despite many attempts over the years, it has not yet been possible to make tetrataenite on anything approaching an industrial scale.

Now, Greer and his colleagues from the Austrian Academy of Sciences and the Montanuniversität in Leoben, have found a possible alternative that doesn’t require millions of years of cooling or neutron irradiation.

The team were studying the mechanical properties of iron-nickel alloys containing small amounts of phosphorus, an element that is also present in meteorites. The pattern of phases inside these materials showed the expected tree-like growth structure called dendrites.

“For most people, it would have ended there: nothing interesting to see in the dendrites, but when I looked closer, I saw an interesting diffraction pattern indicating an ordered atomic structure,” said first author Dr. Yurii Ivanov, who completed the work while at Cambridge and is now based at the Italian Institute of Technology in Genoa.

At first glance, the diffraction pattern of tetrataenite looks like that of the structure expected for iron-nickel alloys, namely a disordered crystal not of interest as a high-performance magnet. It took Ivanov’s closer look to identify the tetrataenite, but even so Greer says it’s strange that no one noticed it before.

The researchers say that phosphorus, which is present in meteorites, allows the iron and nickel atoms to move faster, enabling them to form the necessary ordered stacking without waiting for millions of years. By mixing iron, nickel and phosphorus in the right quantities, they were able to speed up tetrataenite formation by between 11 and 15 orders of magnitude, such that it forms over a few seconds in simple casting.

“What was so astonishing was that no special treatment was needed: we just melted the alloy, poured it into a mold, and we had tetrataenite,” said Greer. “The previous view in the field was that you couldn’t get tetrataenite unless you did something extreme, because otherwise you’d have to wait millions of years for it to form. This result represents a total change in how we think about this material.”

While the researchers have found a promising method to produce tetrataenite, more work is needed to determine whether it will be suitable for high-performance magnets. The team are hoping to work on this with major magnet manufacturers.

The work may also force a revision of views on whether the formation of tetrataenite in meteorites really does take millions of years.

Neurodegenerative diseases like Alzheimer’s, Parkinson’s or Huntington’s disease are characterized by the deposition of protein clumps, so-called protein aggregates, in the brains of patients. Even though disease-relevant proteins—such as the huntingtin protein in Huntington’s disease—are present in all cells of the human brain, aggregates of huntingtin form in a specific region of the brain during the initial stage of the disease.

A recent study by the group of Ulrich Hartl from the Max Planck Institute of Biochemistry investigates the influence, that the cell type has on this preference of aggregate formation in a distinct brain region. The study has been published in the scientific journal Molecular Cell. To address this phenomenon, the researchers performed experiments in a yeast model system.

Artificial protein aggregation through blue light illumination

Similar to the human brain, the formation of huntingtin aggregates in yeast also depend on the cell type, the so-called yeast strain. While the huntingtin protein forms aggregates in some yeast strains, it remains soluble in others. Why this is the case hasn’t been understood so far.

To investigate the distinction between different yeast strains and how they contribute to the formation of huntingtin aggregates, the researchers utilized recent advances in the field of optogenetics. They biotechnologically manipulated yeast strains that normally do not allow the aggregation of huntingtin and integrated a molecular switch that could be activated with blue light. This way, huntingtin aggregates could be formed simply by illuminating the cells with blue light.

Comparing the yeast cells that naturally form huntingtin aggregates with those, that only do so after their activation with blue light, caught the researchers by surprise. Only in cells where huntingtin aggregates already form naturally, but not in those where the aggregation of huntingtin was artificially induced with blue light, were toxic effects observed.

The first author of the study, Michael Gropp, reasoned that this phenomenon came about because smaller intermediates, rather than large aggregates, are the actual toxic version of the protein. Only in yeast cells that form huntingtin aggregates naturally, do these smaller toxic intermediates, the oligomers, exist. Here, large aggregates arise slowly, through the accumulation of proteins around the smaller intermediates.

These small intermediates are bypassed when the aggregation of huntingtin is induced artificially with blue light. Large aggregates then appear much more rapidly, avoiding toxic effects.

The role of prions during aggregate formation

But why do some yeast strains form huntingtin aggregates, while other genetically identical strains do not? Further assays in yeast and experiments with purified proteins—proteins that were artificially enriched in a test tube—helped the researchers to understand this phenomenon. Some yeast strains naturally contain protein aggregates of certain proteins, the prions.

These prion aggregates are not harmful for the cells. However, due to their specific structure, these prion aggregates can influence soluble huntingtin proteins and impose their structure on them. As a result, soluble huntingtin proteins convert into an aggregated state. A side effect of this process is the appearance of toxic intermediates. Yeast strains that naturally do not form huntingtin aggregates also do not possess prions and are therefore unable to generate toxic intermediates, despite the artificial induction of large huntingtin aggregates with blue light.

Possible implications for human disease

In recent years, many human proteins have been characterized that share similarities with the prions in yeast. A bioinformatic analysis of previously published data sets from mouse models and human cell cultures showed that mammalian proteins with such prion-like characteristics preferentially accumulate in neurons.

With the increasing age of an individual, they tend to form aggregates. The authors of the study suspect that the aggregates of these prion-like proteins can in turn force the aggregation of disease-relevant proteins, such as huntingtin, in certain brain areas and thus contribute to the disease progression in neurodegenerative disorders. Further investigation of this hypothesis is still ongoing.

A new type of material can learn and improve its ability to deal with unexpected forces thanks to a unique lattice structure with connections of variable stiffness, as described in a new paper by my colleagues and me.

The new material is a type of architected material, which gets its properties mainly from the geometry and specific traits of its design rather than what it is made out of. Take hook-and-loop fabric closures like Velcro, for example. It doesn’t matter whether it is made from cotton, plastic or any other substance. As long as one side is a fabric with stiff hooks and the other side has fluffy loops, the material will have the sticky properties of Velcro.

My colleagues and I based our new material’s architecture on that of an artificial neural network—layers of interconnected nodes that can learn to do tasks by changing how much importance, or weight, they place on each connection. We hypothesized that a mechanical lattice with physical nodes could be trained to take on certain mechanical properties by adjusting each connection’s rigidity.

To find out if a mechanical lattice would be able to adopt and maintain new properties—like taking on a new shape or changing directional strength—we started off by building a computer model. We then selected a desired shape for the material as well as input forces and had a computer algorithm tune the tensions of the connections so that the input forces would produce the desired shape. We did this training on 200 different lattice structures and found that a triangular lattice was best at achieving all of the shapes we tested.

Once the many connections are tuned to achieve a set of tasks, the material will continue to react in the desired way. The training is—in a sense—remembered in the structure of the material itself.

We then built a physical prototype lattice with adjustable electromechanical springs arranged in a triangular lattice. The prototype is made of 6-inch connections and is about 2 feet long by 1½ feet wide. And it worked. When the lattice and algorithm worked together, the material was able to learn and change shape in particular ways when subjected to different forces. We call this new material a mechanical neural network.

Besides some living tissues, very few materials can learn to be better at dealing with unanticipated loads. Imagine a plane wing that suddenly catches a gust of wind and is forced in an unanticipated direction. The wing can’t change its design to be stronger in that direction.

The prototype lattice material we designed can adapt to changing or unknown conditions. In a wing, for example, these changes could be the accumulation of internal damage, changes in how the wing is attached to a craft or fluctuating external loads. Every time a wing made out of a mechanical neural network experienced one of these scenarios, it could strengthen and soften its connections to maintain desired attributes like directional strength. Over time, through successive adjustments made by the algorithm, the wing adopts and maintains new properties, adding each behavior to the rest as a sort of muscle memory.

This type of material could have far reaching applications for the longevity and efficiency of built structures. Not only could a wing made of a mechanical neural network material be stronger, it could also be trained to morph into shapes that maximize fuel efficiency in response to changing conditions around it.

So far, our team has worked only with 2D lattices. But using computer modeling, we predict that 3D lattices would have a much larger capacity for learning and adaptation. This increase is due to the fact that a 3D structure could have tens of times more connections, or springs, that don’t intersect with one another. However, the mechanisms we used in our first model are far too complex to support in a large 3D structure.

The material my colleagues and I created is a proof of concept and shows the potential of mechanical neural networks. But to bring this idea into the real world will require figuring out how to make the individual pieces smaller and with precise properties of flex and tension.

We hope new research in the manufacturing of materials at the micron scale, as well as work on new materials with adjustable stiffness, will lead to advances that make powerful smart mechanical neural networks with micron-scale elements and dense 3D connections a ubiquitous reality in the near future.

A joint research team led by Prof. Pan Xiulian, Prof. Bao Xinhe and Prof. Hou Guangjin from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) revealed the reaction mechanism of ketene transformation to gasoline on the zeotype H-SAPO-11.

The study was published in Journal of the American Chemical Society on Oct. 3.

In 2016, the team proposed a new catalyst concept based on metal oxide-zeolite bifunctional catalysts and ketene intermediate was detected by highly sensitive synchrotron-based vacuum ultraviolet photoionization mass spectrometry during syngas conversion.

Further studies demonstrated that ketene can be converted to mixed light olefins over molecular zeotype SAPO-34 and transformed to ethene over the eight-membered ring side pocket acid sites of mordenite. Although ketene has also been identified as an important intermediate in other zeolite-catalyzed C1 chemistry, its transformation mechanism is not well understood.

In this study, the researchers studied ketene conversion over H-SAPO-11 employing kinetic analyses, in situ infrared spectroscopy, and solid-state nuclear magnetic resonance spectroscopy.

They found that ketene transformed to butene on the acid sites via either acetyl species following an acetic acid ketonization pathway or acetoacetyl species with keto-enol tautomerism following an acetoacetic acid decarboxylation pathway in the presence of water.

“Our study revealed experimentally for the first time on the reaction network of catalytic ketene conversion over zeotypes and may benefit the further understanding of C1 chemistry,” said Prof. Pan.

Creating a hydrogen economy is no small task, but Rice University engineers have discovered a method that could make oxygen evolution catalysis in acids, one of the most challenging topics in water electrolysis for producing clean hydrogen fuels, more economical and practical.

The lab of chemical and biomolecular engineer Haotian Wang at Rice’s George R. Brown School of Engineering has replaced rare and expensive iridium with ruthenium, a far more abundant precious metal, as the positive-electrode catalyst in a reactor that splits water into hydrogen and oxygen.

The lab’s successful addition of nickel to ruthenium dioxide (RuO₂) resulted in a robust anode catalyst that produced hydrogen from water electrolysis for thousands of hours under ambient conditions.

“There’s huge industry interest in clean hydrogen,” Wang said. “It’s an important energy carrier and also important for chemical fabrication, but its current production contributes a significant portion of carbon emissions in the chemical manufacturing sector globally. We want to produce it in a more sustainable way, and water-splitting using clean electricity is widely recognized as the most promising option.”

Iridium costs roughly eight times more than ruthenium, he said, and it could account for 20% to 40% of the expense in commercial device manufacturing, especially in future large-scale deployments.

The process developed by Wang, Rice postdoctoral associate Zhen-Yu Wu and graduate student Feng-Yang Chen, and colleagues at the University of Pittsburgh and the University of Virginia is detailed in Nature Materials.

Water splitting involves the oxygen and hydrogen evolution reactions by which polarized catalysts rearrange water molecules to release oxygen and hydrogen. “Hydrogen is produced by the cathode, which is a negative electrode,” Wu said. “At the same time, it has to balance the charge by oxidizing water to generate oxygen on the anode side.”

“The cathode is very stable and not a big problem, but the anode is more prone to corrosion when using an acidic electrolyte,” Chen said. “Commonly used transition metals like manganese, iron, nickel and cobalt get oxidized and dissolve into the electrolyte.

“That’s why the only practical material used in commercial proton exchange membrane water electrolyzers is iridium,” he said. “It’s stable for tens of thousands of hours, but it’s very expensive.”

Setting out to find a replacement, Wang’s lab settled on ruthenium dioxide for its known activity, doping it with nickel, one of several metals tried.

The researchers demonstrated that ultrasmall and highly crystalline RuO2 nanoparticles with nickel dopants, used at the anode, facilitated water-splitting for more than 1,000 hours at a current density of 200 milliamps per square centimeter with negligible degradation.

They tested their anodes against others of pure ruthenium dioxide that catalyzed water electrolysis for a few hundred hours before beginning to decay.

The lab is working to improve its ruthenium catalyst to slot into current industrial processes. “Now that we’ve reached this stability milestone, our challenge is to increase the current density by at least five to 10 times while still maintaining this kind of stability,” Wang said. “This is very challenging, but still possible.”

He sees the need as urgent. “The annual production of iridium won’t help us to produce the amount of hydrogen we need today,” Wang said. “Even using all the iridium globally produced will simply not generate the amount of hydrogen we will need if we want it to be produced via water electrolysis.

“That means we can’t fully rely on iridium,” he said. “We have to develop new catalysts to either reduce its use or eliminate it from the process entirely.”