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Category: chemistry

Brain enzyme caught doing something unexpected—it builds polysialic acid on itself

A chance discovery at Nagoya University in Japan has shown that a well-known brain enzyme has a hidden ability: It builds a sugar chain on itself, becomes secreted from the cell and deactivates, then switches on outside the cell once the chain is removed. The finding, published in the Journal of Biological Chemistry, overturns a decades-old assumption about how polysialic acid, a sugar chain critical for brain development and function, is produced and shows a new way an enzyme can regulate its own activity.

The human brain is covered in sugar chains, or glycans, molecular structures that coat cells and regulate how they communicate. One of the most important is polysialic acid, a long chain found mainly in the brain.

Polysialic acid keeps brain cells from adhering too tightly to each other and binds to growth factors and neurotrophins to regulate the presentation of their receptors. Through this, it plays a key role in learning, memory and neural development. Importantly, these sugar chains change rapidly in response to brain activity. The ability to restore them quickly is thought to be essential for normal brain function.

Diamond-based particle detector captures one-picosecond electron bursts for high-rate beam diagnostics

Physicists at UC Santa Cruz and other institutes across California and New Mexico have developed a detection system that will allow next-generation particle accelerators to better reveal fundamental biological and chemical processes, as well as advance critical areas such as materials science and energy research.

The Advanced Accelerator Diagnostics Collaboration, a group of two University of California campuses and three U.S. national laboratories, came together to solve a growing need for high-rate beam diagnostics. These accelerators will now jump from 120 pulses a second to 1 million pulses a second, straining current beam diagnostic systems. The results are now published in the journal Physical Review Accelerators and Beams.

“It really highlights the power of collaboration between universities and national laboratories,” said Bruce Schumm, the Long Family Professor of Experimental Physics. “If you took away Lawrence Berkeley Lab, if you took away Los Alamos, if you took away UC Davis, any of those, the whole thing would have fallen apart.”

How to train your magnet: Excitons as a new knob for magnetic control

Scientists can learn a lot about a quantum material by watching how it responds to light. In magnetic semiconductors, one especially useful messenger is the exciton: a pairing of a negatively charged electron and the positively charged “hole” it leaves behind. Until now, excitons in magnetic materials have mostly been used as reporters. They could reveal how spins were arranged or how magnetic waves moved through a material. But Cornell researchers have shown that excitons can do more than observe magnetism. They can actively steer it.

In the paper “Excitonic Spin Torque in a Magnetic Semiconductor,” published June 15 in Nature Materials, Youn Jue (Eunice) Bae, assistant professor of chemistry and chemical biology in the College of Arts and Sciences, and colleagues report that excitons created by light can exert a spin torque in the two-dimensional magnetic semiconductor chromium sulfide bromide, or CrSBr. The finding establishes excitons as a new way to control magnetic motion with light.

“Excitons have been very useful for watching what spins are doing in magnetic materials,” Bae said. “What we show here is that excitons can also act back on the spins. They are not just spectators; they can help drive the magnetic motion.”

Reversible chirality switching in MoS₂ generates spin currents without magnets

A newly developed method allows researchers to dynamically switch chirality—a particular lack of mirror symmetry—to generate spin currents in semiconductors, researchers from Science Tokyo report. Their approach relies on the reversible insertion and removal of small chiral molecules from the interlayer gaps of a layered, nonchiral semiconductor material using electrochemistry.

The findings could pave the way for the development of novel chiral spintronic materials and technologies that do not rely on magnets or magnetic fields.

New plasma trick could unlock smaller, more powerful computer chips

Under carefully controlled conditions, particles within a plasma can strike the surface of a TMD material and knock atoms loose. The challenge is achieving enough energy to remove sulfur atoms from the top layer without harming the molybdenum layer beneath. Because the difference between success and damage is so small, developing a reliable process has proven difficult.

Using computer simulations, researchers found that treating molybdenum disulfide with oxygen or fluorine before plasma exposure can make the process much more controlled. Their findings were published in the Journal of Physical Chemistry Letters.

Intermolecular collisions may explain why organic radical fluids become unusually magnetic

Certain substances can become magnetic when exposed to an external magnetic field. Magnetic susceptibility measures how easily a material can be magnetized. Materials known as organic radicals have been noted to possess anomalously large magnetic susceptibility. However, researchers have been unable to explain this phenomenon using conventional theories.

Now, researchers at the University of Osaka have developed a theoretical framework to explain this anomalous magnetic susceptibility. This discovery was recently published in the Journal of Physical Chemistry Letters.

Bacteria reveal ‘glue’ protein that fastens antibiotic-resistant outer membrane to cell wall

Researchers at the University of Notre Dame and collaborators have discovered a key process in how the outer membrane of gram-negative bacteria attaches to the cell wall, advancing the understanding of how these bacteria frequently develop resistance to antibiotics.

The research, published in the Journal of the American Chemical Society, was carried out in the laboratory of Shahriar Mobashery, Navari Professor of Life Sciences in the Department of Chemistry and Biochemistry, with structural aspects of the study performed by Juan A. Hermoso of the Institute of Physical Chemistry “Blas Cabrera” in Madrid, Spain. The researchers discovered that the protein PA2854 performs the reaction that keeps the outside layers, or envelope, of gram-negative bacteria connected to each other.

Mobashery and collaborators studied the process in Pseudomonas aeruginosa (P. aeruginosa), a ubiquitous antibiotic-resistant bacterium commonly affecting people with cystic fibrosis. P. aeruginosa, like other gram-negative bacteria including E. coli, Klebsiella pneumoniae and Salmonella, is shielded by a three-layer biological envelope that prevents many antibiotics from penetrating and damaging the bacteria. Gram-positive bacteria do not have an outer membrane and are generally more susceptible to antibiotics.

Beyond frozen snapshots, protein ‘breathing’ comes into view with combined imaging methods

Advances in structural biology have allowed scientists to determine molecular structures with atomic-level detail, sometimes yielding static snapshots that do not reflect the dynamism of proteins. However, these motions are often crucial for biological function. Researchers from the Institute of Science and Technology Austria (ISTA), together with international collaborators, have now combined several methods to shed light on how proteins “breathe” and how some experimental techniques freeze their motion. The findings—which could boost protein design approaches and improve AI-based structural prediction tools—are published in Nature Chemistry.

Despite serving as structural biology’s central pillar for more than half a century, protein crystallography has yielded static molecular structures—like still frames from a video—far from the buzzing life inside cells.

“How much can these ‘frozen snapshots’ of protein structures really tell us about their true biological functions and bustling molecular environments?” asks Lea Becker, the study’s first author and a Ph.D. student in Professor Paul Schanda’s group at the Institute of Science and Technology Austria (ISTA).

Unique chromium beam experiment unlocks cosmic ray origins and galactic chemistry

When a star dies, it generates an explosion of elemental nuclei and hurls them into space. Those elements, called cosmic rays, travel at nearly the speed of light, and eventually some of them encounter manmade detectors. Recording how many of each of these elements show up helps scientists better understand cosmic processes—but despite incredible research advances over the last century, uncertainty around how these elements transform as they travel across the light-years has left fundamental questions about our galaxy’s composition unanswered.

Priyarshini Ghosh, a UMBC nuclear physicist with the Center for Space Sciences and Technology, is at the forefront of research that could significantly improve our understanding of these cosmic phenomena.

Ghosh and her collaborators have just completed a pioneering experiment at the Facility for Rare Isotope Beams (FRIB) at Michigan State University, where they generated and then fragmented a beam of chromium-52 nuclei. Chromium-52 is of particular interest because it can shed light on different processes happening in our galaxy, and yet it has never been measured.

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