Graphical abstract portraying the development of the LitChemPlast database. Credit: Wiesinger et al. 2024; DOI: 10.1021/acs.estlett.4c00355
Plastics contain a vast number of chemicals, some of which greatly impact the environment and human health. However, information on the presence of individual substances in plastic products is oftentimes not publicly available.
In a study, published on 29 October 2024, in Environmental Science and Technology Letters, a new publicly accessible database on chemicals measured in plastics is presented—LitChemPlast. The database contains over 3,500 substances measured in over 47,000 samples of plastic products across 372 studies.
The database shows that, due to inadequate control measures, mechanical recycling of plastics often leads to contamination with hazardous substances. For example, brominated flame retardants have frequently been detected in toys.
LitChemPlast is a significant step forward for better understanding of chemicals’ movement through different life stages of plastics. The database provides real-world chemical data, including on concentrations in products, that is useful for improving models estimating human and environmental exposure to plastic chemicals.
Moreover, LitChemPlast enables researchers, regulators and practitioners to identify chemicals that are of interest for regulation, to find safer materials for recycling, and to trace plastic pollution back to its source. It may also assist in identifying hazardous chemicals that are non-intentionally added to plastics (so called NIAS).
LitChemPlast also highlights research gaps, such as limited regional coverage in low- and middle-income countries, a lack of nontargeted measurements for non-food packaging categories, and a narrow focus on well-known hazardous chemicals.
Future concerted efforts in these understudied areas are essential to support the transition toward a safe and sustainable circular plastics economy, including achieving full transparency of chemicals in plastics.
The open database can serve as a starting point for guiding future research on identifying and quantifying chemicals in plastics, develop policy measures for ensuring safer material cycles, and support researchers, regulators and practitioners in better understanding the flow of chemicals throughout plastic products’ life cycles.
Finally, the authors encourage the scientific and regulatory communities to continue developing and using the database which is part of the larger PlastChem database that was published earlier in 2024.
Helene Wiesinger, Ph.D., currently scientific officer at the Food Packaging Forum and corresponding author of the study said, “Many scientific efforts focus only on whether plastics comply with current regulations, rather than whether they are actually safe. This is worrying because there are many chemicals in plastics that are not yet adequately regulated, meaning that potential risks could slip through the cracks.”
Zhanyun Wang, Ph.D., Scientist at Empa—Swiss Federal Laboratories for Materials Science and Technology and corresponding author of the study said, “Transparency of chemicals in plastics is crucial for ensuring safer material cycles, protecting human and environmental health, and fostering a sustainable circular economy.
“LitChemPlast marks a significant step in this direction, and we encourage widespread collaboration to further expand and refine this valuable resource.”
More information: LitChemPlast: An open database of chemicals measured in plastics, Environmental Science & Technology Letters (2024). DOI: 10.1021/acs.estlett.4c00355
Penn State professor of chemistry Joseph Cotruvo, Jr. and graduate student Wonseok Choi have been researching ways to separate rare earth elements using reengineered bacterial proteins that are found in nature. Credit: Michelle Bixby/Penn State
A newly discovered protein naturally houses an unusual binding site that can differentiate between rare earth elements, and researchers at Penn State have made it even better. Rare earth elements are key components used in everything from modern tech to gasoline production. The protein, called LanD, enriches neodymium and praseodymium over other similar rare earth elements (REEs) and has the potential to revolutionize industrial mining, researchers said.
Scientists at Penn State, led by professor of chemistry Joseph Cotruvo, Jr., recently published their LanD discovery in the Proceedings of the National Academy of Sciences.
“Each rare earth element has specific properties that make it useful for different applications, yet they are notoriously difficult to separate from each other,” said Cotruvo, who has filed a patent application related to the work. “Current industrial methods are inefficient and require heavy use of toxic chemicals, so a protein-based method for rare earth mining could make this process more efficient, greener, and less expensive.”
Close to 80% of the United States’ REE supply is imported, according to the United States International Trade Commission. Cotruvo explained that there is plenty of domestic raw material—including recycling old tech and industrial byproducts—to source REEs, but not all REEs are of equal value and application.
A more effective separation approach could help secure a national supply of REEs. The 17 REEs, including 15 metals called “lanthanides,” are commonly divided into “light” and “heavy” groups, with the light REEs being far more abundant. Unfortunately, however, the most common light REEs, lanthanum and cerium, have little value, whereas the other light REEs, praseodymium and (in particular) neodymium, are much more valuable.
Neodymium is a critical component of permanent magnets used in smartphones and renewable energy machinery like wind turbines, and praseodymium is often combined with neodymium for these applications.
Cotruvo’s lab previously identified another protein, LanM, that binds to all REEs with high specificity over any other metal. It does this in a fashion similar to a lock and key mechanism, with the protein being the lock and the REE a key. When the protein binds a REE, it undergoes a change in shape analogous to the key turning in the lock. The LanM proteins studied to date are very good at differentiating between heavy REEs, but they do not do well separating the light REEs, akin to a keyhole that fits a few different keys.
The newly discovered LanD protein, however, has improved separation abilities among the light REEs that are as good as, if not better than, current industry practices, Cotruvo said. With a unique, never-before-seen binding site—where the metal “key” can lock into the protein—LanD’s natural REE separation abilities can be engineered to be even more efficient, offering new hope for a greener rare earth element mining industry, he said.
“Current efforts are concentrated towards optimizing REE separation to make it less labor and material intensive,” Cotruvo said. “But this organism, Methylobacterium extorquens, a bacterium found abundantly in nature, makes proteins that seem to have already solved the problem.”
Methylobacterium extorquens is a species of bacteria known for its ability to grow on one-carbon compounds like methanol, and prefers to use specific REEs, mostly lanthanum and cerium, to support that growth.
When Cotruvo discovered LanM as the first high-affinity, high-specificity REE-binding protein six years ago, it was not clear why LanM needed to bind REEs so tightly in the cell. The discovery of LanD suggested an answer to that question: the two proteins work in tandem, with LanD binding to the lanthanides that the bacterium takes up but doesn’t need and delivering them to LanM, where they are sequestered. Those lanthanides, while not important to the bacteria, are the ones that are most important to tech production, Cotruvo said.
“The bacterium can take up a broader group of lanthanides than the small subset that it prefers to use, so it needs a way to prevent those undesirable lanthanides from interfering with the functions of the desirable lanthanides in the cell,” Cotruvo said. “LanD and LanM appear to work together to do this sorting, which explains why the previously identified LanM protein is good at lanthanide separations in general.”
He added that LanD, with its unique binding site, is much better for the light REEs specifically.
“LanD conveniently binds best to neodymium, which is by far the most valuable of the light REEs,” Cotruvo said. “While the naturally occurring LanD protein exhibits a preference for neodymium, we re-engineered it to more effectively be able to extract neodymium from a mixed solution of light REEs, disfavoring the other REEs that are of lesser value.”
The researchers found that engineering the LanD binding site allows separations yielding the desired neodymium and praseodymium to become much more effective. In future applications, the researchers said they hope to be able to whittle down the protein size and increase the preference of this binding site even more—and implement it in a larger-scale separation. The site can serve as the starting point for chemists and engineers to develop highly specific proteins to perfect sorting of other tricky-to-separate elements, Cotruvo said.
Furthermore, because LanD and LanM specialize in separation of different REEs, they could be used together in a process to separate complex REE sources like ores.
“The LanD protein is a promising way to improve REE separation practices,” he said. “And we’re working on making it even better, to pave a path toward more effective, greener rare earth mining.”
Paper co-authors include Wyatt Larrinaga and Jonathan Jung, graduate students in chemistry; Chi-Yun Lin, postdoctoral researcher in chemistry; and Amie Boal, professor of chemistry and of biochemistry and molecular biology.
More information: Wyatt B. Larrinaga et al, Modulating metal-centered dimerization of a lanthanide chaperone protein for separation of light lanthanides, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2410926121
Motivated to turn greenhouse gases like carbon dioxide into high value chemicals like methanol, EPFL chemical engineers have developed a new method to make catalysts. Catalysts are major tools in the chemical industry and are largely made to make petrochemicals.
In this method, they have developed a way to build—with near atomic precision—metal clusters on solid supports that have the potential to improve catalytic activity. The results are published in Nature Catalysis.
“You want to produce as much product per time per catalyst as possible, and we’ve found that when a catalyst is prepared with near atomic precision, you get a more active material,” says Jeremy Luterbacher, professor at EPFL’s Laboratory of Sustainable and Catalytic Processing. “This technique is particularly interesting for difficult reactions like that of carbon dioxide with hydrogen gas for producing renewable methanol.”
A bit about catalysts
Though they are ubiquitous in industry, we most commonly interact with solid catalysts in the tailpipe of our car. There, a catalytic converter takes the exhaust from fuel combustion and helps to reduce the amount of toxic pollutants released into the air.
The engine of a car notably produces carbon monoxide (CO), an odorless and colorless toxic gas that, in high concentrations, can cause illness and death if inhaled. Inside the chamber is a catalyst, usually made of small platinum or palladium particles on a cheaper solid. This metal binds air and pollutants like carbon monoxide, and helps them react to produce the less toxic carbon dioxide (CO2) gas into the air.
“A reaction can happen without a catalyst at high temperature. For instance, burning carbon monoxide in a flame makes it possible for the carbon monoxide and oxygen to crash together to form carbon dioxide because they’re hot enough for the collision to be sufficiently powerful,” explains Luterbacher.
“With a catalyst, the carbon monoxide and the oxygen are bound to a metal surface and they can react despite colliding at a lower temperature. It’s like they’re ice-skating on the surface of the catalyzer and the surface helps the transformation between the pollutant and the reactant along.”
The catalysts of the future need to be able to turn carbon dioxide, a greenhouse gas that’s the largest source of renewable carbon on our planet, into high value gases like methanol. This process takes place in a chemical reaction referred to as a hydrogenation, a difficult reaction since it can produce many things other than methanol. Making a catalyst that is active enough to transform carbon dioxide fast enough to methanol without making other products is a significant challenge.
Precision layering of the catalyst
To make a solid catalyst, a metal particle is deposited on top of a material with high surface area like a porous powder, to maximize contact with the reactant.
Luterbacher and his team wondered if they could control and speed up reactions by precisely controlling the catalyst composition, notably by choosing just the right amount of material to tune how tightly reactants would bind to the catalyst.
They had discovered in previous research that they could deposit islands of metals with near atomic precision on solid supports, a method called liquid-phase atomic layer deposition (ALD), perfect for creating precise catalyst active sites for enabling a reaction.
Indeed, depositing these small islands or clusters of several metals with near atomic precision allowed the EPFL team to hydrogenate carbon dioxide at rates that were more than 10 times higher than with a catalyst of the same composition but built without this control.
They used magnesium oxide as the support, which usually binds carbon dioxide too tightly to be reactive, and they deposited small zirconia islands, which is a material that usually binds carbon dioxide too lightly. Then, they added copper to bind the hydrogen. When placed together in just the right proportions, they seemed to have the right mix to make a lot of methanol quickly and little of anything else.
“Magnesium oxide is widely recognized as a stable material for CO2 capture, but its strong affinity for CO2 has limited its use as a catalyst support. We turned this limitation into an opportunity by teaming it up with zirconia.
“Finding the optimal balance for CO2 affinity by combining MgO and ZrO2 with differing properties was only achievable through the powerful tool of liquid-phase atomic layer deposition,” says Seongmin Jin, former postdoctoral researcher at LPDC and lead author of the study.
“If we compare the amount of catalyst material to its copper content, then our catalyzer is more active than even commercial catalysts. Our activity per active site is also superior. It’s worth noting that our activity per weight of catalyst material is still inferior to commercial equivalents because we need to figure out how to make many more of these clusters on the surface.
“But we’ve shown that it’s possible to achieve very high control even at the atomic level, and this control appears to be very important. This opens the avenues to explore many combinations of metals or possibilities,” concludes Luterbacher.
More information: Seongmin Jin et al, Atom-by-atom design of Cu/ZrOx clusters on MgO for CO2 hydrogenation using liquid-phase atomic layer deposition, Nature Catalysis (2024). DOI: 10.1038/s41929-024-01236-y
A new benchmark for electronic structure calculations with graphics processing units has been achieved. Credit: Nathan Johnson | Pacific Northwest National Laboratory
A recent collaboration among researchers from HUN-REN Wigner Research Center for Physics in Hungary and the Department of Energy’s Pacific Northwest National Laboratory, along with industry collaborators SandboxAQ and NVIDIA, has achieved unprecedented speed and performance in efforts to model complex metal-containing molecules.
The collaboration resulted in 2.5 times the performance improvement over previous NVIDIA graphics processing unit (GPU) calculations and 80 times the acceleration compared to similar calculations using central processing unit (CPU) methods. The research study, recently published in the Journal of Chemical Theory and Computation, sets a new benchmark for electronic structure calculations.
Accelerating molecular modeling
The research team’s efforts have enabled unprecedented calculations for complex biochemical systems, which include transition metal metalloenzymes. Such metal-containing catalysts are crucial in numerous industrial and biological processes, playing an essential role in facilitating chemical reactions.
These powerhouses of energy conversion are vital for many industries, including medicine, energy and consumer products. They accelerate chemical reactions, lowering the energy required and making processes more efficient and sustainable. Understanding and optimizing these catalysts is essential for addressing global challenges, such as clean energy production and environmental sustainability.
“When you have one or more metals in your system, then you have a lot of electronic states that are very close in energy, but behave differently, and that’s why it’s really important to make sure that you describe them accurately,” said Sotiris Xantheas, a PNNL Lab Fellow, a co-author of the research study, and a chemical physicist who leads the Center for Scalable and Predictive methods for Excitation and Correlated phenomena (SPEC), as well as the Computational and Theoretical Chemistry Institute at PNNL.
Highly correlated quantum chemistry calculations
The recent advances have been made possible by bringing together academic and industry experts with expertise in the development of tensor network state algorithms and high performance computing, led by Örs Legeza, a co-PI of the SPEC project, and his group at the HUN-REN Wigner Research Center for Physics, in Hungary, working with SandboxAQ’s team of scientists, led by co-author Martin Ganahl, to perform quantum chemistry calculations on NVIDIA GPUs.
The diverse team contributions underscore the importance of collaboration and point to an exciting future for the field powered by GPUs. For instance, this work implemented the ab initio Density Matrix Renormalization Group method, which describes physical properties of large, complex electronic structures on all GPUs within a single node for the first time.
The goal of the research was to achieve efficient and accurate solutions to the many-body Schrödinger equation. These algorithms are crucial for understanding the electronic structures of molecules and materials and require computational power only available on a few computing systems worldwide.
The group’s collective expertise and shared resources have helped push the boundaries of quantum chemistry, allowing for rapid iteration and refinement in the study of highly correlated complex chemical systems. The project illustrates the potential of large-scale calculations to revolutionize how scientists approach challenging quantum chemistry problems.
“With advancing computational hardware and the extension to multi-GPU, multi-node architectures are expected to enable even more comprehensive calculations beyond the current capabilities,” said Legeza, who also holds an appointment as a research fellow at the Institute for Advanced Study at the Technical University of Munich.
“The ongoing collaboration aims to adopt large-scale GPU-accelerated calculations, further enhancing the efficiency and accuracy of quantum chemistry computations, utilizing even more recent hardware developments.”
As noted in the published study, chemists today largely rely on their intuition because rapid, highly accurate calculations are often unattainable. The ability to quickly iterate on different choices of large active spaces enables a more systematic search. Today’s GPU computing frameworks, combined with AI-guided physics and new methods for generating training data for large quantitative machine learning models, are expected to contribute to applications in energy, sustainability and health.
“The combination of NVIDIA’s state-of-the-art hardware with cutting-edge simulation techniques like tensor network algorithms for quantum chemistry has the potential to unlock an entirely new field of discovery,” said Ganahl.
More information: Andor Menczer et al, Parallel Implementation of the Density Matrix Renormalization Group Method Achieving a Quarter petaFLOPS Performance on a Single DGX-H100 GPU Node, Journal of Chemical Theory and Computation (2024). DOI: 10.1021/acs.jctc.4c00903
UV irradiation of diacetylene crystals obtained by forming a unique array structure changes the luster from silver to gold. Credit: Michinari Kohri from Chiba University
There have been many attempts to create monochromatic metallic materials, but few materials change luster color in response to external stimuli. In a recent breakthrough, researchers from Chiba University have prepared a diacetylene derivative-based metallic luster material that changes from silver to gold under UV irradiation.
These findings are expected to find applications in decorative items, printing inks, photomask patterning, UV laser lithography, and cosmetics.
Societies of the past and present have given high regard to precious metals like gold and silver. Both metals remind us of nobility and luxury. However, they are quite expensive, which restricts their applications. Therefore, materials with attractive but artificial gold- and silver-like metallic lusters are popular, finding use in jewelry, reflective materials, inks, and cosmetics.
Unfortunately, typical metallic luster materials cause environmental harm, rendering them unsustainable. Thus, scientists are actively searching for metal-free alternatives, examining organics such as thiophene, pyrrole, porphyrin, azobenzene, and stilbene derivatives. They have found some success in creating materials whose colors can be tuned by external stimuli while maintaining the metallic luster. However, the task still remains challenging.
Recently, a group of researchers from Chiba University, led by Professor Michinari Kohri and Kyoka Tachibana from the Graduate School of Engineering, in collaboration with scientists from Mitsubishi Pencil Co., Ltd., Tokyo University of Science, Keio University, and Yamagata University, has demonstrated the preparation of a metallic luster material that changes color from silver to gold under UV irradiation.
Their findings were published in ACS Applied Materials & Interfaces on September 14, 2024.
Highlighting the motivation behind this study, Prof. Kohri says, “Expanding on our earlier findings on biomimetic metallic luster materials, we conducted a targeted search for molecular structures capable of transitioning between silver and gold. This effort resulted in the identification of a novel material with desirable properties.”
In this study, researchers developed diacetylene (DA) derivative-based luster materials incorporating stilbenes via linkers at both ends, denoted as DS-DAn (where n represents the linker carbon number, ranging from 1 to 6). Varying n yielded diverse metallic luster and color change behaviors.
After several innovative experimental trials, the researchers observed that the stacked structure of platelet crystals comprising DS-DA1, the derivative with the shortest linker carbon chain, had a silver look. Its luster notably turned to gold upon UV irradiation, a remarkable external stimulus-based behavior.
The team attributed this to the unique crystal structure of DS-DA1 with two coexisting assembled states, revealing that partial topochemical polymerization (a polymerization method performed by monomers that are aligned in the crystal state) of DA within the structure modified its color tone from silver to gold.
The silver luster material developed in this study can express a golden luster selectively in specific areas using only light irradiation. It is also possible to add gradation colors of gold and silver. Thus, it has the potential to be useful in a variety of applications, such as decorative items, printing inks, and cosmetics.
“By eliminating metal components, our innovative material minimizes environmental footprint and weight. Moreover, its suitability for UV laser-based drawing techniques opens up new possibilities for high-end decorative printing. Further exploration of molecular structures may make it possible to express a wider variety of glossy colors,” concludes Prof. Kohri.
This work advances the fundamental science of DA polymerization and unlocks new opportunities for metallic luster materials with desirable properties in photomask patterning and UV laser lithography.
More information: Kyoka Tachibana et al, Silver to Gold Metallic Luster Changes in Stimuli-Responsive Diacetylene Derivatives Uniquely Arranged within Crystals, ACS Applied Materials & Interfaces (2024). DOI: 10.1021/acsami.4c14218
The living ship, viewed from midships towards the bow. Scenes projected into the hull reflect activities performed in each area. The ‘players’ are the volunteers and staff, clad in copies of clothing and using replicas of artifacts. To the left is the main deck gallery containing the real artifacts, positioned opposite where they were found during the excavation. The sloping walkway follows the line of the main deck. Credit: Hufton + Crow; The Mary Rose Trust via Dr. Alex Hildred, CC-BY 4.0 (creativecommons.org/licenses/by/4.0/)
A new study of human skeletal remains from the wreck of the 16th century English warship “Mary Rose” suggests that whether a person is right- versus left-handed may influence how their clavicle bone chemistry changes as they age. Dr. Sheona Shankland of Lancaster University, U.K., and colleagues present these findings in the open-access journal PLOS ONE on October 30, 2024.
The Mary Rose was part of the Tudor navy during Henry VIII’s reign. On July 19, 1545, it sank while engaging French ships in the Battle of the Solent. Excavated in the late 20th century, the ship’s artifacts and the crew’s skeletal remains were notably well preserved, allowing for extensive research into the belongings, appearance, and health of the crew members.
Now, Dr. Shankland and colleagues contribute new insights into the biology of 12 men aged 13 to 40 who sank with the ship. This work explored how the chemistry of bone might adjust in response to physical activity and aging, so a person’s bone chemistry may hold clues about their lifestyle.
In this case, the researchers analyzed human clavicles (collarbones) from the wreck using a non-destructive laser technique called Raman spectroscopy to reveal bone chemistry.
The analysis focused on organic proteins and inorganic minerals, as they are the two main components of bone. It revealed that, among the 12 men, mineral content increased with age, while protein content decreased, albeit to a lesser degree.
These age-related changes were more pronounced in right clavicles than in left clavicles. A higher proportion of people are naturally right- than left-handed, and at the time when the Mary Rose sank, left-handedness was associated with witchcraft and therefore strongly discouraged.
So, assuming right-handed preference among the crew, this finding suggests that handedness may have affected their clavicle chemistry, perhaps through putting more stress on their right side during repeated ship-related activities.
The authors note that more research on the Mary Rose clavicles will be needed to better understand these findings. Nonetheless, this study could contribute to ongoing understanding of handedness and age-related changes in bone chemistry, with potential implications for risk of fracture, osteoarthritis, and other bone conditions.
Dr. Sheona Shankland adds, “Having grown up fascinated by the Mary Rose, it has been amazing to have the opportunity to work with these remains. The preservation of the bones and the non-destructive nature of the technique allows us to learn more about the lives of these sailors, but also furthers our understanding of the human skeleton, relevant to the modern world.”
Dr. Jemma Kerns adds, “It has been a privilege to work with these unique and precious human remains to learn more about life for sailors in the 16th century while finding out more about changes to bone composition as we age, which is relevant to today’s health, has been fascinating.”
Prof. Adam Taylor adds, “This study sheds new light on what we know about the clavicle and its mineralization. The bone plays a critical role in attaching your upper limb to the body and is one of the most commonly fractured bones.”
Dr. Alex Hildred adds, “Our museum is dedicated to the men who lost their lives defending their country. The hull is surrounded on three sides by galleries containing their possessions, and we continue to explore their lives through active research. The non-destructive nature of Raman spectroscopy makes it an ideal research tool for investigating human remains.
“We are delighted that the current research undertaken by Lancaster Medical School not only provides us with more information about the lives of our crew, but also demonstrates the versatility of Raman. The fact that this research has tangible benefits today, nearly 500 years after the ship sank, is both remarkable and humbling.”
More information: Shining light on the Mary Rose: Identifying chemical differences in human aging and handedness in the clavicles of sailors using Raman spectroscopy, PLOS ONE (2024). DOI: 10.1371/journal.pone.0311717
How the structure of a halide perovskite is distorted when it interacts with chiral molecules. Credit: National Renewable Energy Laboratory
A research team has discovered a new process to induce chirality in halide perovskite semiconductors, which could open the door to cutting-edge electronic applications.
The development is the latest in a series of advancements made by the team involving the introduction and control of chirality. Chirality refers to a structure that cannot be superimposed on its mirror image, such as a hand, and allows greater control of electrons by directing their “spin.” Most traditional optoelectronic devices in use today exploit control of charge and light but not the spin of the electron.
The researchers have been able to create a spin-polarized LED using chiral perovskite semiconductor in the absence of extremely low temperatures and a magnetic field, as was previously reported. The newest advance accelerates the materials development process for spin control.
The details are spelled out in a new paper, “Remote Chirality Transfer in Low-Dimensional Hybrid Metal Halide Semiconductors,” which is published in the journal Nature Chemistry. The key was in introducing a chiral molecule with a different headgroup into the perovskite.
The chiral molecule intentionally does not fit into the perovskite lattice but “twists” the structure from the surface. The chiral molecule transfers its properties several unit cells or layers deep into the perovskite structure. This twist can be controlled by employing left- or right-handed chiral molecules into the grain boundaries and surfaces of a perovskite film, which control the spin properties accordingly.
Remote chirality transfer in hybrid metal halides. Credit: Nature Chemistry (2024). DOI: 10.1038/s41557-024-01662-2
Such twisted structures enable unique functionalities for energy applications where spin-control adds additional potential by acting as electronic spin filters.
Md Azimul Haque, the first author of the paper, said introducing chirality to the low-dimensional perovskite semiconductors generally includes a chiral molecule being present in the perovskite lattice, which needs extensive analysis every time one changes the composition of the chiral molecule.
The ability of a proximal chiral molecule to transfer its properties without changing the perovskite composition makes the process simple, faster, and less limiting on the composition, he said.
“We can create materials with known properties now with added chirality very easily compared to traditional methods,” said Haque, a postdoctoral researcher. “The next step is to experiment with the materials and incorporate them into new applications.”
Hybrid perovskites refer to a crystalline structure, containing both inorganic and organic components. In other semiconductors, such as those made from silicon, the material is purely inorganic and rigid. Hybrid perovskites are soft and more flexible, “so a twisting molecule on the surface, will extend the effect deeper into this semiconductor than it can in most rigid, inorganic semiconductors,” said Joey Luther, a National Renewable Energy Laboratory (NREL) senior research fellow and corresponding author.
“This is a new way to induce chirality in halide perovskites,” Luther said, “and it could lead to technologies that we can’t really envision but might be somewhere along the lines of polarized cameras, 3D displays, spin information transfer, optical computation, or better optical communication—things of that nature.”
More information: Md Azimul Haque et al, Remote chirality transfer in low-dimensional hybrid metal halide semiconductors, Nature Chemistry (2024). DOI: 10.1038/s41557-024-01662-2
Graphical Abstract. Credit: Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202415124
Increasing amounts of data require storage, often for long periods. Synthetic polymers are an alternative to conventional storage media because they maintain stored information while using less space and energy. However, data retrieval by mass spectrometry limits the length and thus the storage capacity of individual polymer chains.
In the journal Angewandte Chemie International Edition, researchers have introduced a method that overcomes this limitation and allows direct access to specific bits without reading the entire chain.
Data accumulates constantly, resulting from business transactions, process monitoring, quality assurance, or tracking product batches. Archiving this data for decades requires much space and energy. For long-term archival of large amounts of data that requires infrequent access, macromolecules with a defined sequence, like DNA and synthetic polymers, are an attractive alternative.
Synthetic polymers have advantages over DNA: simple synthesis, higher storage density, and stability under harsh conditions. Their disadvantage is that the information encoded in polymers is decoded by mass spectrometry (MS) or tandem-mass sequencing (MS2). For these methods, the size of the molecules must be limited, which severely limits the storage capacity of each polymer chain.
In addition, the complete chain must be decoded in sequence, building block by building block—the bits of interest cannot be accessed directly. It is like having to read through an entire book instead of just opening it to the relevant page. In contrast, long chains of DNA can be cut into fragments of random length, sequenced individually, and then computationally reconstructed into the original sequence.
Kyoung Taek Kim and his team at the Department of Chemistry at Seoul National University have developed a new method by which very long synthetic polymer chains whose molecular weights greatly exceed the analytical limits of MS and MS2 can be efficiently decoded.
As a demonstration, the team encoded their university address into ASCII and translated this—together with an error detection code (CRC, an established method used to ensure data integrity)—into a binary code, a sequence of ones and zeroes.
This 512-bit sequence was stored in a polymer chain made of two different monomers: lactic acid to represent a 1 and phenyllactic acid to represent a 0. At irregular intervals, they also included fragmentation codes containing mandelic acid. When chemically activated, the chains break at those locations.
In their demonstration, they obtained 18 fragments of various sizes that could be individually decoded by MS2 sequencing.
Specially developed software initially identified the fragments based on their mass and their end groups, as shown by the MS spectra. During the MS2 process, previously measured molecular ions break down further, and these pieces were then also analyzed.
The fragments could be sequenced based on the mass difference of the pieces. With the aid of the CRC error detection code, the software reconstructed the sequence of the entire chain, overcoming the length limit for the polymer chains.
The team was also able to decode interesting bits without sequencing the entire polymer chain (random access), such as the word “chemistry” in the code for their address.
By taking into account that the parts of their address are all in a specific order (department, institution, city, postal code, country) and separated by commas, they were able to isolate the location where the desired information was stored within the chain and only sequenced the relevant fragments.
More information: Heejeong Jang et al, Shotgun Sequencing of 512‐mer Copolyester Allows Random Access to Stored Information, Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202415124
Cross-section of the food vacuole, the Plasmodium’s stomach-like sac, in which it digests hemoglobin. The image, obtained by cryogenic scanning transmission electron tomography (CSTET), reveals several large kitchen cleaver-shaped crystals of the malaria pigment in the center, and numerous smaller ones on the periphery. Credit: ACS Central Science (2024). DOI: 10.1021/acscentsci.4c00162
Prof. Leslie Leiserowitz first became intrigued by malaria when he was a young boy in South Africa. His father, who scouted the continent in search of wood for the family business, brought back not only tales of elephants and gorillas but also skin rashes and ringing in his ears, side effects of the quinine he took to prevent malaria.
Decades later, while studying crystals at the Weizmann Institute of Science, Leiserowitz realized that malaria was in fact surprisingly pertinent to his research. He learned that the malaria parasite thrives inside red blood cells thanks to its knack for crafting crystals, and he set out to study these crystals, later joining forces with a chemistry faculty colleague, Prof. Michael Elbaum.
A new study—headed by Elbaum and Leiserowitz and conducted in collaboration with prominent research teams around the world—has culminated in a paper that might help outwit the malaria parasite. It reveals in unprecedented detail the structure of crystals that the parasite builds in order to survive.
Since most antimalarial drugs are thought to work by interfering with the formation and growth of these crystals, the new findings might lead to improved antimalarial medications.
The research is published in the journal ACS Central Science.
“There had been enormous advances in imaging technologies such as electron and X-ray microscopy, and we realized that we could apply them to do something good for humanity,” says Elbaum, explaining how this research came about. “It was an opportunity we simply couldn’t pass up.”
Watch how an image of the food vacuole – the Plasmodium’s stomach-like sac, in which the parasite digests hemoglobin – is being constructed using CSTET. A cross-section of the vacuole reveals several large crystals of the malaria pigment in the center, and numerous smaller ones on the periphery
Seeing malaria pigment in a whole new way
Even though the incidence of malaria was drastically slashed in the first two decades of the 21st century, the disease remains an immense global health problem, killing more than half a million people each year, most of them young children. Much of the eradication effort is aimed at controlling the mosquitoes that, through their bites, transmit the malaria parasite—a single-celled organism belonging to the genus Plasmodium.
Antimalarial drugs are also essential to this effort, but many of the existing medications have lost their effectiveness because the parasites have become resistant to them. Improved drugs could help break the cycle of the parasite’s passage from mosquitoes to humans and back.
The production of crystals is a survival trick the parasite uses in its takeover of blood cells. This maneuver enables it to feast on hemoglobin, the oxygen-carrying protein in the blood.
Digesting the hemoglobin releases heme, an iron-containing molecular complex needed for binding oxygen. Freed from the surrounding protein, however, heme is so reactive that it can kill the parasite. That’s precisely why Plasmodium pulls a survival stunt, in which it renders the heme harmless by packaging it into dark-colored crystals known as the malaria pigment, or more technically, as hemozoin.
When it was discovered in the 19th century, hemozoin was initially thought to be made by the patient’s body in response to the infection, but its true origin—through the doings of the parasite—was eventually understood.
In his early studies on hemozoin crystals, Leiserowitz was fascinated by their symmetries, a topic he had worked on for many years with his Weizmann colleague Prof. Meir Lahav. When applied to malaria, this topic becomes a life-and-death matter: The different ways in which heme molecules fit into the crystals not only create different symmetries but can also affect crystal growth, which, in turn, can seal the parasite’s fate. However, such structural nuances were too subtle to be resolved by the methods of the day.
In the meantime, Elbaum had been independently working on Plasmodium from an entirely different angle. Together with colleagues at the Hebrew University of Jerusalem, he was studying Plasmodium cells as they go through their peculiar process of replication.
Whereas most cells divide by splitting in two, the malaria parasite first makes numerous copies of its components within a red blood cell, then instantly divides into multiple daughter parasites that go on to infect new blood cells.
When the scientists explored cellular nuclei during this process using newly available 3D electron microscopy methods, the hemozoin crystals also came into full view. So when Leiserowitz presented his work on these crystals at a faculty meeting, the collaboration with Elbaum was a natural outcome.
The collaboration proved fruitful from the start, thanks in large part to emerging new technologies for probing matter on the nanoscale. In their very first joint study, the scientists shed new light on crystal formation using soft X-ray tomography, a method that Elbaum had helped develop during a sabbatical in Berlin.
Then, a new approach to cryo-electron tomography that Elbaum developed with Weizmann and colleagues enabled the study of intact cells in which the malaria pigment is manufactured.
As luck would have it, a new lab working on the biology of the malaria parasite opened at Weizmann. It supplied Elbaum and Leiserowitz with infected red blood cells from which the hemozoin could be extracted.
Revealing the structure of these natural crystals was crucial for medical applications, particularly because existing structural knowledge had been largely based on the more readily available synthetic crystals, used in most previous hemozoin studies.
But the crystals did not divulge their secrets easily. Searching for pieces of the structure puzzle that were still missing after a detailed three-dimensional analysis at Weizmann, Elbaum and Leiserowitz sent their pigment samples to colleagues at the University of Oxford and the Diamond Light Source (the UK’s national synchrotron) who had installed a new method of electron crystallography that produced astounding images of the pigment.
Having finished their initial analysis, the British scientists suggested securing the collaboration of researchers elsewhere.
“From then on, the research turned into a relay race of sorts, with each lab suggesting involving colleagues with top expertise in additional fields,” Elbaum recalls. “The group finally expanded to a kind of all-star team for increasingly sophisticated analysis.”
Ultimately, the list of study authors came to comprise 17 researchers from Israel, the UK, Austria, the Czech Republic and the United States. That is, it took a coalition of some of the world’s most advanced labs and a battery of the latest technologies to unravel the survival savvy honed over the course of evolution by a bunch of single-celled blood parasites.
Answering the question of the ugly crystals
The result of this international collaboration—a definitive, atom-by-atom three-dimensional structure of the malaria pigment—supplied a host of valuable insights. For starters, it solved a puzzle generated by previous studies, in which the Weizmann scientists had observed crystals of a peculiar trapezoid shape that resembled a kitchen cleaver: The “blade” end was always smooth and sharp, like a chisel, while the “handle” end was variable and often jagged.
“We were wondering how nature could produce something so ugly—these crystals looked as if they’d been bitten on one side,” Leiserowitz recalls.
The detailed structure resolved the kitchen cleaver quandary. Heme molecules fit into the malaria pigment crystals in pairs, but because the “front” and “back” faces of these molecules differ chemically, they can pair up vis-à-vis one another in four distinct ways. In other words, there are four distinct heme building blocks, or basic units, of hemozoin crystals.
Two of these are symmetric, but the other two are chiral, which means that they are mirror images of one another and cannot be superimposed, like the left and the right hand.
When they grow together in a single crystal, the result can be an atomically disordered surface, including a jagged end. Such clear understanding of the crystal surfaces is essential to designing or evaluating drugs that must bind to the crystal to inhibit its growth.
Drugs can attain their goal in ways that are more complex than stopping crystal growth, but the stoppage is vital for those other effects too.
Leiserowitz explains the complexity using a car factory analogy: “Imagine that you are churning out cars, say, 500 a day, but at the end of the line, the drivers who have to take these cars away stop working, so all those cars pile up. That’s exactly what happens when a drug prevents heme molecules from moving on to join a crystal. They pile up and jam the membranes, so nothing can get in or out, which helps to kill the parasite.”
The study can facilitate the design of new drugs by making it much easier to, for example, calculate the interactions between crystals and the medication. In addition, the findings clarified which facets of the crystals grow more rapidly than others and identified facets whose growth is most likely to be inhibited by drug binding.
Finally, the study revealed subtle but essential differences between natural and synthetic malaria crystals, which underscores the importance of designing future drugs on the basis of structural information about real-life crystals made by the parasite.
Elbaum presented the study’s findings at the symposium “Leslie at 90: A Scientific Odyssey,” held at Weizmann to mark Leiserowitz’s 90th birthday. Of course, the publication of the paper coincided with this milestone birthday merely by chance, but it surely served as a grand reward for some two decades of Leiserowitz’s research on the malaria pigment and for his life-long interest in malaria.
More information: Paul Benjamin Klar et al, Cryo-tomography and 3D Electron Diffraction Reveal the Polar Habit and Chiral Structure of the Malaria Pigment Crystal Hemozoin, ACS Central Science (2024). DOI: 10.1021/acscentsci.4c00162
Helical wheel diagrams of; (A) K47; and (B) K311. Helical wheels generated using HeliQuest (https://heliquest.ipmc.cnrs.fr/). (C) Sequences of K47 and K311 aligned with the heptad abcdefg and hendecad abcdefghijk registers. Credit: Biomacromolecules (2024). DOI: 10.1021/acs.biomac.4c00661
Peptides come and peptides go, sometimes too fast. These strings of amino acids—the building blocks of life—are of intense interest to researchers for their potential to treat everything from stroke to infection, either as the drug or the drug delivery vehicle. That is, when they last long enough to do their work.
“Peptides are potentially powerful components of medicines, because they’re just fragments of our natural proteins that our bodies can recognize,” said University of Virginia assistant professor of chemical engineering Rachel Letteri. “But one limitation is that they tend to break down quickly, so we need to figure out how to make them more stable.”
Letteri’s lab, led by her Ph.D. advisee Vincent Gray, has demonstrated an approach for overcoming the longevity problem by designing mirror images of natural peptides called coiled coils.
Coiled coils, helix-shaped peptides resembling curly ribbons twisted together, are found in nearly 10% of the proteins in many organisms. They play critical roles in preparing proteins to properly carry out their jobs, in part by pulling together multiple copies of proteins.
“This happens when individual helices in a protein recognize their match and bind in a specific way, forming the coiled coil,” Letteri said. “It’s like puzzle pieces fitting together. This binding is crucial for proteins to work as they should.”
Proteins help build and repair the body, oxygenate the blood, regulate digestion and perform a host of other functions.
The binding and connecting features of coiled coils make them especially tantalizing as components for medicines, including biomaterials for tissue regeneration. Yet, like other natural peptides, they degrade quickly.
Coiled coil mirrors extend peptide life
Previous research has shown that blending natural peptides with their mirror images results in excellent binding and stability. Gray and Letteri wondered if the strategy would also work with coiled coils. Could the team design mirrored coiled coils, with all their medicinal promise, to improve both their specific binding ability and longevity for medicinal use?
Gray and Letteri found that compared to natural coiled coil combinations in which the two strands spiral in same direction, their engineered coils—with the two strands spiraling in opposite directions—indeed showed stronger binding and greater longevity in biological environments.
Why does it work? Mirror-image peptides improve stability because they are not affected by enzymes that accelerate chemical breakdown of natural peptides. Moreover, the mirror images can be designed to target natural peptides and bind tightly in specific ways due to their opposite but complimentary shape—much like intertwining the fingers of your left and right hands.
While the team successfully demonstrated the concept, the research has a long way to go, Letteri said.
“Researchers are just beginning to understand how to engineer peptides to leverage specific interactions between peptides and their mirror images,” she said. “We hope that these specific, long-lasting interactions between mirror-image peptides will unlock new design tools for next-generation therapeutics and biomaterials.”
More information: Vincent P. Gray et al, Designing Coiled Coils for Heterochiral Complexation to Enhance Binding and Enzymatic Stability, Biomacromolecules (2024). DOI: 10.1021/acs.biomac.4c00661
