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Category: chemistry – Page 16

Genomic reorganization at the transition to gametogenesis

Using a technique called Hi-C analysis, which looks at how DNA is arranged in three dimensions inside the nucleus, the team found that at this transitional point the genome’s three-dimensional organisation becomes less structured and chromosomes become more separated inside the nucleus.

Creating sperm and eggs in the laboratory (in vitro) remains one of the greatest challenges in reproductive biology. To study this process, scientists use primordial germ cell–like cells (PGCLCs), which are lab-generated cells derived from embryonic stem cells that mimic the embryo’s earliest reproductive cells. However, these PCGLCs often fail to complete all the steps of meiosis, making it difficult to create functional sperm and eggs in petri dishes.

After studying the process in germ cells from the embryos, the team studied lab-generated mouse PCGLCs to see if the centromeres migrated to the periphery of the nucleus in vitro too, but they did not see the same phenomenon.

“The presence of this chromosome conformation in embryonic germ cells, but not lab-grown cells, suggests that this structural change could be required for meiosis to proceed properly, and could explain why meiosis is so difficult to recreate outside the body,” says the author, “but we need to do more work to fully characterise the process before we can say for sure.”

“Our study has uncovered a previously unknown and frankly very surprising restructuring of genome architecture that occurs in developing germ cells, which we believe is critical for a successful execution of meiosis,” says the senior author. ScienceMission sciencenewshighlights.

In our cells, our DNA carries chemical or ‘epigenetic’ marks that decide how genes will be used in different tissues. Yet in the group of specialised cells, known as ‘germ cells’, which will later form sperm and eggs, these inherited chemical instructions must be erased or reshuffled so development can begin again with a fresh blueprint in future generations.

Continue reading “Genomic reorganization at the transition to gametogenesis” | >

Gut bacteria can sense their environment and it’s key to your health

Your gut bacteria are chemical detectives—sniffing out nutrients and even feeding each other to keep your microbiome thriving. Your gut is home to trillions of bacteria that constantly “sense” their surroundings to survive and thrive. New research shows that beneficial gut microbes, especially common Clostridia bacteria, can detect a surprisingly wide range of chemical signals produced during digestion, including byproducts of fats, proteins, sugars, and even DNA. These microbes use specialized sensors to move toward valuable nutrients, with lactate and formate standing out as especially important fuel sources.

The gut microbiome, also called the gut flora, plays a vital role in human health. This enormous and constantly changing community of microorganisms is shaped by countless chemical exchanges, both among the microbes themselves and between microbes and the human body. For these interactions to work, gut bacteria must be able to detect nutrients and chemical signals around them. Despite their importance, scientists still know relatively little about the full range of signals that bacterial receptors can recognize.

A key question remains. Which chemical signals matter most to beneficial gut bacteria?

Astronomers shocked by how these giant exoplanets formed

JWST just found evidence that some “super-Jupiters” may have formed like planets, not failed stars. A distant star system with four super-sized gas giants has revealed a surprise. Thanks to JWST’s powerful vision, astronomers detected sulfur in their atmospheres — a chemical clue that they formed like Jupiter, by slowly building solid cores. That’s unexpected because these planets are far bigger and orbit much farther from their star than models once allowed.

Gas giants are enormous planets made primarily of hydrogen and helium. They may contain dense central cores, but unlike Earth, they do not have solid surfaces you could stand on. In our solar system, Jupiter and Saturn are classic examples. Beyond our neighborhood, astronomers have identified many gas giant exoplanets, some far larger than Jupiter. The most massive of these worlds begin to resemble brown dwarfs, substellar objects sometimes called “failed stars” because they do not fuse hydrogen.

This overlap raises a major question in astronomy. How exactly do these massive planets form? One possibility is core accretion, the same process believed to have created Jupiter and Saturn. In this scenario, a solid core slowly builds up inside a disk of dust and ice, gathering rocky and icy material until it becomes massive enough to pull in surrounding gas. Another possibility is gravitational instability, where a swirling cloud of gas around a young star collapses quickly under its own gravity, forming a large object more like a brown dwarf.

Interplay between cancer cell lipotypes and disease states

Lipid metabolism in cancer.

Cancer cells exhibit distinct lipotypes to sustain functional states crucial for tumorigenesis.

Various lipid metabolism components like biosynthesis, uptake, storage, and degradation of lipids contribute to cancer cell fitness.

Cancer cells dynamically transition across lipotypes under microenvironmental stress.

Targeting essential nodes in lipid metabolism may offer novel cancer therapeutics. sciencenewshighlights ScienceMission https://sciencemission.com/cancer-cell-lipotypes

While the initial transformation of cancer cells is driven by genetic alterations, tumor cell behaviors and functional states are dynamically regulated by cell-intrinsic factors including proteins, metabolites and lipids, and extrinsic microenvironmental factors. Emerging multi-omics technologies highlighted that cancer cells exhibit distinct lipidome compositions and employ specific lipid metabolic circuits for chemical conversions – collectively defined as ‘lipotypes’. We review the interplay between cancer lipotypes and cellular states, focusing on interpreting how being at different positions along the spectra of representative lipid metabolic axes influences cancerous traits. We aim to instill a system biology perspective to integrate ‘lipotypes’ into the established ‘genotype–phenotype’ framework in cancer.

Continue reading “Interplay between cancer cell lipotypes and disease states” | >

High-Pressure Freezing EM Tomography of Entire Ribbon Synapses in the Retina

JNeurosci: Using advanced electron microscopy in rats, Zhang et al. captured 3D images of chemical synapses that perform visual computations in the retina. Their findings reveal how neural connections are structured for efficient visual signaling.

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In the retina, presynaptic active zones in photoreceptors and bipolar cells are distinguished by a plate-like “ribbon” linked to the plasma membrane (PM) and surrounded by dozens of synaptic vesicles (SVs) tethered to it. SVs at the base of the ribbon, closest to the PM, are thought to constitute the readily releasable vesicle pool (RRP), i.e., SVs primed to be released 1–2 ms following stimulation. The number of SVs in the RRP is a critical synaptic parameter that influences synaptic strength and varies with light levels to enable ribbon synapses to compute visual information. Physiological RRP measurements agree well with anatomical estimates obtained via electron microscopy (EM), although EM often employs chemical fixation, which causes exocytotic artifacts that may influence RRP size.

Scientists Uncover the Secret Structure Behind “Nature’s Proton Highway”

Phosphoric acid is vital in both biology and modern technology because of its exceptional ability to move electrical charge. Inside the human body and in devices such as fuel cells, this small molecule helps drive essential chemical reactions.

Scientists at the Department of Molecular Physics at the Fritz Haber Institute have now uncovered new details about how it performs this task at the molecular level.

The Nervous System and Behavior

Many central issues with which neurosciences is concerned, such as how we perceive the world around us, how we learn from experience, how we remember, how we direct our movements, and how we communicate with each other, have commanded the attention of thoughtful men and women for centuries. But it was not until after World War II that neuroscience began to emerge as a separate and increasingly vigorous scientific discipline that has as its ultimate objective providing a satisfactory account of animal (including human) behavior in biological terms. This ambitious goal has as its basis the central realization that all behavior is, in the last analysis, a reflection of the function of the nervous system. It is the organized and coordinated activity of the nervous system that ultimately manifests itself in the behavior of the organism. The challenge to neuroscience then, is to explain, in physical and chemical terms, how the nervous system marshalls its signaling units to direct behavior.

The real magnitude of this challenge can perhaps be best judged by considering the structural and functional complexity of the human brain and the bewildering complexity of human behavior. The human brain is thought to be composed of about a hundred billion (1011) nerve cells and about 10 to 50 times that number of supporting elements or glial cells. Some nerve cells have relatively few connections with other neurons or with such effector organs as muscles or glands, but the great majority receive connections from thousands of other cells and may themselves connect with several hundred other neurons. This means that at a fairly conservative estimate the total number of functional connections (known as synapses) within the human brain is on the order of a hundred trillion (1014). But what is most important is that these connections are not random or indiscriminate:

They constitute the essential “wiring” of the nervous system on which the extraordinarily precise functioning of the brain depends. We owe to the great neuroanatomists of the last century, and especially to Ramón y Cajal, the brilliant insight that cells with basically similar properties are able to produce very different actions because they are connected to each other and to the sensory receptors and effector organs of the body in different ways. One major objective of modern neuroscience is therefore to unravel the patterns of connections within the nervous system—in a word, to map the brain.

From theory to safety: New model predicts how combustion scenarios unfold

Researchers from Skoltech have published a paper in the journal Physica D: Nonlinear Phenomena presenting an analysis of steady propagating combustion waves—from slow flames to supersonic detonation waves. The study relies on the authors’ mathematical model, which captures the key physical properties of complex combustion processes and yields accurate analytical and numerical solutions. The findings are important for understanding the physical mechanisms behind the transition from deflagration to detonation, as well as for developing safer engines, fuel combustion systems, and protection against unwanted explosions in industrial settings.

The scientists identified several main types of combustion waves. The most powerful is strong detonation —a supersonic shock wave that sharply compresses and heats the mixture, triggering a chemical reaction. This type of wave is highly stable. In weak detonations and weak deflagration waves, there is no abrupt shock front.

The chemical reaction only begins if the mixture has been preheated to a temperature where it can ignite. These regimes occur rarely, under specific conditions, and can easily break down or transition into another wave type.

New technique spots hidden defects to boost reliability of ultrathin electronics

Future devices will continue to probe the frontier of the very small, and at scales where functionality depends on mere atoms, even the tiniest flaw matters. Researchers at Rice University have shown that hard-to-spot defects in a widely used two-dimensional insulator can trap electrical charges and locally weaken the material, making it more likely to fail at lower voltages. The findings are published in Nano Letters.

“By showing practical ways to detect when and where these defects form, we help make future devices more reliable and repeatable,” said Hae Yeon Lee, an assistant professor of materials science and nanoengineering at Rice, who is a corresponding author on the study.

Building ultrathin electronics such as advanced transistors, photodetectors and quantum devices involves stacking sheets of different 2D materials on top of each other into “heterostructures.” Hexagonal boron nitride (hBN), prized for being atomically flat and chemically stable, is a common building block.

‘Solar battery’ stores sunlight for days, then releases hydrogen on demand

A new material can store energy from sunlight and convert it into hydrogen days later. The material, jointly developed by researchers from Ulm and Jena, can do this even in the dark. The process is reversible and can be reactivated several times using a pH switch. The results are published in the journal Nature Communications.

Green hydrogen is one of the most important pillars of the energy transition. It is produced from sunlight using photocatalytic processes. There are now a variety of technologies for converting and storing solar energy into chemical energy. But now, for the first time, a material that can store the energy from sunlight for several days and then release it in the form of hydrogen “at the push of a button” has been successfully developed.

“You can think of it as a combination of a solar cell and a battery at the molecular level,” explains Professor Sven Rau, who heads the Institute of Inorganic Chemistry I at Ulm University.

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