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Category: chemistry – Page 254

Researchers identify African dust

Every summer, weather forecasters blast news about African dust plumes crossing the southern United States. And to most people, it’s just dust, but to researchers at Texas A&M University, it’s much more.

Researchers have developed a new method called isotope-resolved chemical mass balance to identify dust participles using isotopic measurements. Their new research builds off previous studies where they identified and quantified the dust by determining the .

The study was recently published in Environmental Science & Technology.

Caltech-led Research Team Finds Traditional Computers Can Solve Some Quantum Problems

PRESS RELEASE — There has been a lot of buzz about quantum computers and for good reason. The futuristic computers are designed to mimic what happens in nature at microscopic scales, which means they have the power to better understand the quantum realm and speed up the discovery of new materials, including pharmaceuticals, environmentally friendly chemicals, and more. However, experts say viable quantum computers are still a decade away or more. What are researchers to do in the meantime?

A new Caltech-led study in the journal Science describes how machine learning tools, run on classical computers, can be used to make predictions about quantum systems and thus help researchers solve some of the trickiest physics and chemistry problems. While this notion has been shown experimentally before, the new report is the first to mathematically prove that the method works.

“Quantum computers are ideal for many types of physics and materials science problems,” says lead author Hsin-Yuan (Robert) Huang, a graduate student working with John Preskill, the Richard P. Feynman Professor of Theoretical Physics and the Allen V. C. Davis and Lenabelle Davis Leadership Chair of the Institute for Quantum Science and Technology (IQIM). “But we aren’t quite there yet and have been surprised to learn that classical machine learning methods can be used in the meantime. Ultimately, this paper is about showing what humans can learn about the physical world.”

3D metal complexes could be the answer to overcoming fungal drug-resistance

Scientists discover that 1 in 5 metal compounds display anti-fungal properties-they are non-toxic too.

Metal compounds could be the answer to the growing problem of drug-resistant fungal infections, according to new research published in the American Chemical Society on Sept .23.

The compounds could help develop much-needed antifungal drugs-particularly for immunocompromised patients susceptible to fungal infections.

Nanopore-based technologies beyond DNA sequencing

Ideally, the nanopore dimensions should be comparable to those of the analyte for the presence of the analyte to produce a measurable change in the ionic current amplitude above the noise level. Nanopores can be formed in several ways, with a wide range of pore diameters. Biological nanopores are formed by the self-assembly of either protein subunits, peptides or even DNA scaffolds in lipid bilayers or block copolymer membranes1,3,6,17,18. They possess atomically precise dimensions controlled by biopolymer sequences, providing the ability to recognize biomolecules with constriction diameters of ~1–10 nm. Solid-state nanopores are crafted in thin inorganic or plastic membranes (for example, SiNx), which allows the nanopores to have extended diameters of up to hundreds of nanometres, permitting the entry or analysis of large biomolecules and complexes. The tools for fabricating solid-state nanopores, which include electron/ion milling4,5, laser-based optical etching19,20 and the dielectric breakdown of ultrathin solid membranes21,22, can be used to manipulate nanopore size at the nanometre scale, but allow only limited control over the surface structure at the atomic level in contrast to biological nanopores. The chemical modification and genetic engineering of biological nanopores, or the introduction of biomolecules to functionalize solid-state nanopores23, can further enhance the interactions between a nanopore and analytes, improving the overall sensitivity and selectivity of the device2,17,24,25,26. This feature allows nanopores to controllably capture, identify and transport a wide variety of molecules and ions from bulk solution.

Nanopore technology was initially developed for the practicable stochastic sensing of ions and small molecules2,27,28. Subsequently, many developmental efforts were focused on DNA sequencing1,7,8,9. Now, however, nanopore applications extend well beyond sequencing, as the methodology has been adapted to analyse molecular heterogeneities and stochastic processes in many different biochemical systems (Fig. 1). First, a key advantage of nanopores lies in their ability to successively capture many single molecules one after the other at a relatively high rate, which allows nanopores to explore large populations of molecules at the single-molecule level in reasonable timeframes. Second, nanopores essentially convert the structural and chemical properties of the analytes into a measurable ionic current signal, even achieving enantiomer discrimination29. The technology can be used to report on multiple molecular features while circumventing the need for labelling chemistries, which may complicate the overall analysis process and affect the molecular structures. For example, nanopores can discriminate nearly 13 different amino acids in a label-free manner, including some with minute structural differences30. An important aspect is the ability of nanopores to identify species31 that lack suitable labels for signal amplification or whose information is hidden in the noise of analytical devices. Consequently, nanopores may serve well in molecular diagnostic applications required for precision medicine, which achieves the identification of nucleic acid, protein or metabolite analytes and other biomarkers11,32,33,34,35. Third, nanopores provide a well-defined scaffold for controllably designing and constructing biomimetic systems, which involve a complex network of biomolecular interactions. These nanopore systems track the binding dynamics of transported biomolecules as they interact with nanopore surfaces, hence serving as a platform for unravelling complex biological processes (for example, the transport properties of nuclear pore complexes)36,37,38,39. Fourth, chemical groups can be spatially aligned within a protein nanopore, providing a confined chemical environment for site-selective or regioselective covalent chemistry. This strategy has been used to engineer protein nanoreactors to monitor bond-breaking and bond-making events40,41.

Here we discuss the latest advances in nanopore technologies beyond DNA sequencing and the future trajectory of the field, as well as the opportunities and main challenges for the next decade. We specifically address the emerging nanopore methods for protein analysis and protein sequencing, single-molecule covalent chemistry, single-molecule analysis of clinical samples and insights into the use of biomimetic pores for analysing complex biological processes.

Scientists break down silk to invent extremely efficient non-stick material

The new material is far superior to today’s non-stick options.

Researchers at Tufts University have developed a method for developing silk-based materials that refuse to stick to water and exhibit non-stick properties that surpass those of current non-stick surfaces, according to a press release by the institution published on Friday.

“The success we had with modifying silk to repel water extends our successes with chemically modifying silk for other functionalities—such as the ability to change color, conduct electrical charge, or persist or degrade in a biological environment,” said David Kaplan, Stern Family Professor of Engineering at Tufts.

“As a protein, silk lends itself well to modular chemistry – the ability to ‘plug in’ different functional components on a natural scaffold.”

In addition to being implemented in medical devices, the new material could have uses as automotive windshields where rainwater just rolls off without using wipers, coatings on metals that help prevent rust, or on fabrics to make them easier to clean.

Substances trapped in nanobubbles exhibit unusual properties

Skoltech scientists modeled the behavior of nanobubbles appearing in van der Waals heterostructures and the behavior of substances trapped inside the bubbles. In the future, the new model will help obtain equations of state for substances in nano-volumes, opening up new opportunities for the extraction of hydrocarbons from rock with large amounts of micro-and nanopores. The results of the study were published in the Journal of Chemical Physics.

The van der Waals nanostructures hold much promise for the study of tiniest samples with volumes from 1 cubic micron down to several cubic nanometers. These atomically thin layers of two-dimensional materials, such as graphene, (hBN) and dichalcogenides of transition metals, are held together by weak van der Waals interaction only. Inserting a sample between the layers separates the upper and bottom layers, making the upper layer lift to form a nanobubble. The resulting will then become available for transmission electron and , providing an insight into the structure of the substance inside the bubble.

The properties exhibited by inside the van der Waals nanobubbles are quite unusual. For example, water trapped inside a nanobubble displays a tenfold decrease in its dielectric constant and etches the diamond surface, something it would never do under normal conditions. Argon which typically exists in when in large quantities can become solid at the same pressure if trapped inside very small nanobubbles with a radius of less than 50 nanometers.

Physicists make molecular vibrations more detectable

In molecules, the atoms vibrate with characteristic patterns and frequencies. Vibrations are therefore an important tool for studying molecules and molecular processes such as chemical reactions. Although scanning tunneling microscopes can be used to image individual molecules, their vibrations have so far been difficult to detect.

Physicists at Kiel University (Christian-Albrechts-Universität zu Kiel, CAU) have now invented a method with which the vibration signals can be amplified by up to a factor of 50. Furthermore, they increased the frequency resolution considerably. The new method will improve the understanding of interactions in molecular systems and further simulation methods. The research team has now published the results in the journal Physical Review Letters.

The discovery by Dr. Jan Homberg, Dr. Alexander Weismann and Prof. Dr. Richard Berndt from the Institute of Experimental and Applied Physics, relies on a special quantum mechanical effect, so-called “inelastic tunneling”. Electrons that pass through a molecule on their way from a metal tip to the substrate surface in the scanning tunneling microscope can release energy to the molecule or take energy up from it. This occurs in portions determined by the properties of the respective molecule.

Energy storage materials built from nano-sized molecular blocks

Molecules of the rare metallic element niobium can be used as molecular building blocks to design electrochemical energy storage materials. Mark Rambaran, Department of Chemistry at Umeå University, presents in his thesis a method for producing solid materials from aqueous solutions containing nano-sized niobium molecules, called polyoxoniobates.

“These polyoxoniobates are water-soluble and can be synthesized in large volumes. They act as , in the same way as when a child stacks Lego bricks,” Mark Rambaran says. “They can be used to make a wide range of materials, including supercapacitors that facilitate lithium-ion storage.”

Synthesis of polyoxoniobates can be done with microwave irradiation, because it is a rapid and efficient alternative to conventional hydrothermal methods, Mark Rambaran shows in his thesis.

Traditional computers can solve some quantum problems

There has been a lot of buzz about quantum computers and for good reason. The futuristic computers are designed to mimic what happens in nature at microscopic scales, which means they have the power to better understand the quantum realm and speed up the discovery of new materials, including pharmaceuticals, environmentally friendly chemicals, and more. However, experts say viable quantum computers are still a decade away or more. What are researchers to do in the meantime?

A new Caltech-led study in the journal Science describes how tools, run on , can be used to make predictions about and thus help researchers solve some of the trickiest physics and chemistry problems. While this notion has been shown experimentally before, the new report is the first to mathematically prove that the method works.

“Quantum computers are ideal for many types of physics and materials science problems,” says lead author Hsin-Yuan (Robert) Huang, a graduate student working with John Preskill, the Richard P. Feynman Professor of Theoretical Physics and the Allen V. C. Davis and Lenabelle Davis Leadership Chair of the Institute for Quantum Science and Technology (IQIM). “But we aren’t quite there yet and have been surprised to learn that classical machine learning methods can be used in the meantime. Ultimately, this paper is about showing what humans can learn about the physical world.”

Neuroimaging study suggests mental fatigue helps preserve the chemical integrity of the brain

Strenuous cognitive work leads to an accumulation of glutamate in the prefrontal cortex, according to new research published in the journal Current Biology. The new findings suggest that mental fatigue is a neuropsychological mechanism that helps to avert the build up of potentially toxic byproducts of prolonged cognitive activity.

“Nobody knows what mental fatigue is, how it is generated and why we feel it,” said study author Antonius Wiehler, a member of the Motivation, Brain and Behavior Lab at Pitié Salpêtrière Hospital in Paris. “It has remained a mystery despite more than a century of scientific research. Machines can do cognitive tasks continuously without fatigue, the brain is different and we wanted to understand how and why. Mental fatigue has important consequences: for economic decisions, for management at work, for education at school, for clinical cure, etc.”

The researchers were particularly interested in the role of glutamate, an excitatory neurotransmitter that is involved in a variety of cognitive functions, including learning and memory. In addition, glutamate plays a role in controlling the strength of synaptic connections. Too much or too little glutamate can lead to neuronal dysfunction, so it is critical that this neurotransmitter is tightly regulated.