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Twisting the End Game: How Telomere Chromatin Modifications Shape Telomere Maintenance

Cell division inevitably shortens telomeric DNA owing to the end-replication problem. Eukaryotic chromosomes possess specialized telomere structures to maintain genomic stability. In most proliferative cells, telomerase adds telomeric repeats during S-phase. In differentiated cells where telomerase is silenced, telomeres shorten progressively, thereby compromising genomic integrity. Consequently, cancer cells universally activate alternative telomere maintenance mechanisms during malignant transformation: ~80% reactivate telomerase, while a portion of the rest rely on BIR (break-induced replication)–mediated homologous recombination-based ALT (alternative lengthening of telomeres). Although these mechanisms are stable once established, the initial determinants influencing a cancer cell’s choice remain poorly understood. This review discusses recent molecular insights into how telomeric chromatin properties profoundly impact this choice. After briefly introducing telomere chromatin characteristics and key players in its maintenance and dynamics, we discuss the mechanisms by which cancer cells acquire distinct telomere replication capabilities. In particular, we present an in-depth analysis linking telomere heterochromatin status to ALT. Furthermore, based on recent advances, we propose a coupled feedforward loop model explaining how the ALT state becomes “locked in” once initiated. Finally, we offer novel perspectives on rational, telomere-centric therapeutic interventions for ALT-positive cancers, focusing on strategies designed to disrupt such feedforward loops by manipulating telomeric chromatin structure.

Graphene measurements reveal energy-loss and quantum-coherence exponents diverge under gate control

Scientists have shown that the two exponents (inelastic scattering exponent and dephasing exponent) commonly used to describe electron scattering in graphene do not necessarily follow the same behavior. Using gated epitaxial graphene, a multi-institutional team of researchers independently extracted the two exponents through current-heating measurements and weak-localization analysis. The contrasting gate-voltage dependence provides evidence that energy relaxation and loss of quantum phase coherence can be governed by different microscopic processes.

The team was led by Dr. Wei-Chen Lin at National Taiwan University and collaborating institutions. Their study, published in Carbon, challenges a long-standing assumption that the exponents used to characterize these two processes should be equivalent.

An electron in a solid can lose energy through inelastic scattering, while quantum coherence can be lost when the phase relationship between electron wave functions is disrupted. These two phenomena are closely related, but they do not necessarily provide the same information. In this study, scientists used epitaxial graphene grown on silicon carbide and controlled its carrier density with a gate voltage.

Could negative mass exist and be observed?

Unlike electric charge, as far as we know all mass is positive, and positive masses attract one another. Could negative mass exist, and if so, what would be the ramifications?

Antigravity between a positive mass and a hypothetical negative mass has received a fair bit of attention in both physics and science fiction over the years. For example, in 1901’s “First Men in the Moon” author H. G. Wells imagines a substance he calls “cavorite” which creates a negative force of gravity and thus acts as a gravity shield. In Newton’s theory of gravity, negative mass would effectively appear as his same equation but with the gravitational constant G replaced by-G. But Einstein’s version of gravity, general relativity, is not so kind, and does not seem to consistently allow anti-gravity.

In a new paper in Physics of the Dark Universe, Shin’ichi Nojiri from Japan and S.D. Odintsovc from Spain dig deeper into the possibility of negative mass objects (NMOs) and conclude that the idea may not be as exotic as is thought. Using theoretical tools, they show that negative mass “does not always lead to any inconsistency.”

Scientists build world’s most accurate atomic clock

Take a second and turn it into trillions of moments. Measure each one. That’s how precisely an atomic clock at Singapore’s Centre for Quantum Technologies (CQT) keeps time—and with record-setting accuracy, according to results published in Nature on Sept. 23.

“I am confident that what we have now is the most accurate clock in the world,” says team leader Murray Barrett, a CQT principal investigator and associate professor in the Department of Physics at the National University of Singapore.

The researchers base their claim on measurements showing that their atomic clock, built from the element lutetium, outperforms previous record holders built from different elements.

Quantum device simulates matter popping into existence

A research team led by faculty at the Duke Quantum Center (DQC) has observed string-breaking dynamics related to particle-antiparticle formation on a quantum simulator, among the first such observations in quantum physics.

The approach, described in the journal Nature Physics, shows that trapped-ion quantum computers can be used to probe fundamental questions about the universe. The experiment emulates string-breaking, a phenomenon in which two connected fundamental building blocks of matter stretch apart, building up enough energy that new particles “pop into existence” when the connection snaps.

“Quantum computer simulations provide the best platform to investigate complex questions like matter formation, short of having witnessed the Big Bang itself,” said Christopher Monroe, the Gilhuly Family Presidential Distinguished Professor of Electrical and Computer Engineering and Physics at Duke, who led the research.

New robotic hand can walk, press keys and move objects on its own

For many of us, the last—and only—time we’ve seen a walking hand was Thing in “The Addams Family” movies or TV series. Now there’s another. Engineers from the Soft Robotics Lab at ETH Zurich have adapted an off-the-shelf detached robotic hand so it can crawl across different surfaces, balance and interact with its environment.

But this is no sci-fi gimmick. Fully mobile robotic hands could be useful in hard-to-reach spaces. “A robotic hand with its own mobility could operate in confined workspaces without requiring the arm that normally carries it to follow,” says the research team.

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