Catálogo de publicaciones - revistas

<jats:p>A DNA polymerase with a single mutation and a divalent calcium cofactor catalyzes the synthesis of unnatural N3′→P5′ phosphoramidate (NP) bonds to form NP-DNA. However, this template-directed phosphoryl transfer activity remains orders of magnitude slower than native phosphodiester synthesis. Here, we used time-resolved x-ray crystallography to show that NP-DNA synthesis proceeds with a single detectable calcium ion in the active site. Using insights from isotopic and elemental effects, we propose that one-metal-ion electrophilic substrate activation is inferior to the native two-metal-ion mechanism. We found that this deficiency in divalent activation could be ameliorated by trivalent rare earth and post–transition metal cations, substantially enhancing NP-DNA synthesis. Scandium(III), in particular, confers highly specific NP activity with kinetics enhanced by more than 100-fold over calcium(II), yielding NP-DNA strands up to 100 nucleotides in length.</jats:p>

<jats:p>Synthetic lattices in photonics enable the exploration of light states in new dimensions, transcending phenomena common only to physical space. We propose and demonstrate a quantum walk comb in synthetic frequency space formed by externally modulating a ring-shaped semiconductor laser with ultrafast recovery times. The initially ballistic quantum walk does not dissipate into low supermode states of the synthetic lattice; instead, the state stabilizes in a broad frequency comb, unlocking the full potential of the synthetic frequency lattice. Our device produces a low-noise, nearly flat broadband comb (reaching 100 per centimeter bandwidth) and offers a promising platform to generate broadband, tunable, and stable frequency combs.</jats:p>

<jats:p> The transport of energy and information in semiconductors is limited by scattering between electronic carriers and lattice phonons, resulting in diffusive and lossy transport that curtails all semiconductor technologies. Using Re <jats:sub>6</jats:sub> Se <jats:sub>8</jats:sub> Cl <jats:sub>2</jats:sub> , a van der Waals (vdW) superatomic semiconductor, we demonstrate the formation of acoustic exciton-polarons, an electronic quasiparticle shielded from phonon scattering. We directly imaged polaron transport in Re <jats:sub>6</jats:sub> Se <jats:sub>8</jats:sub> Cl <jats:sub>2</jats:sub> at room temperature, revealing quasi-ballistic, wavelike propagation sustained for a nanosecond and several micrometers. Shielded polaron transport leads to electronic energy propagation lengths orders of magnitude greater than in other vdW semiconductors, exceeding even silicon over a nanosecond. We propose that, counterintuitively, quasi-flat electronic bands and strong exciton–acoustic phonon coupling are together responsible for the transport properties of Re <jats:sub>6</jats:sub> Se <jats:sub>8</jats:sub> Cl <jats:sub>2</jats:sub> , establishing a path to ballistic room-temperature semiconductors. </jats:p>

<jats:p>The understanding of nonequilibrium dynamics in many-body quantum systems is a fundamental issue in statistical physics. Experiments that probe universal properties of these systems can address such foundational questions. In this study, we report the measurement of universal dynamics triggered by a quench from the superfluid to normal phase across the Berezinskii-Kosterlitz-Thouless transition in a two-dimensional (2D) Bose gas. We reduced the density by splitting the 2D gas in two, realizing a quench across the critical point. The subsequent relaxation dynamics were probed with matter-wave interferometry to measure the local phase fluctuations. We show that the time evolution of both the phase correlation function and vortex density obeys universal scaling laws. This conclusion is supported by classical-field simulations and interpreted by means of real-time renormalization group theory.</jats:p>

<jats:p>Functionally similar to the tight junctions present in animal guts, plant roots have evolved a lignified Casparian strip as an extracellular diffusion barrier in the endodermis to seal the root apoplast and maintain nutrient homeostasis. How this diffusion barrier is structured has been partially defined, but its lignin polymerization and assembly steps remain elusive. Here, we characterize a family of dirigent proteins (DPs) essential for both the localized polymerization of lignin required for Casparian strip biogenesis in the cell wall and for attachment of the strip to the plasma membrane to seal the apoplast. We reveal a Casparian strip lignification mechanism that requires cooperation between DPs and the Schengen pathway. Furthermore, we demonstrate that DPs directly mediate lignin polymerization as part of this mechanism.</jats:p>

<jats:p> A new kind of data revolution is unfolding around the world, one that is unlikely to be on the radar of tech giants and the power brokers of Silicon Valley. Indigenous Data Sovereignty (IDSov) is a rallying cry for Indigenous communities seeking to regain control over their information while pushing back against <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://networkcultures.org/blog/2022/12/13/how-to-resist-against-data-colonialism-interview-with-nick-couldry-ulises-mejias/">data colonialism</jats:ext-link> and its myriad harms. Led by Indigenous academics, innovators, and knowledge-holders, IDSov networks now exist in the <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://nni.arizona.edu/our-work/research-policy-analysis/indigenous-data-sovereignty-governance">United States</jats:ext-link> , <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://fnigc.ca/">Canada</jats:ext-link> , <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.temanararaunga.maori.nz/">Aotearoa</jats:ext-link> (New Zealand), <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.maiamnayriwingara.org/">Australia</jats:ext-link> , the <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://pacificdatasovereignty.com/">Pacific</jats:ext-link> , and <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://uit.no/research/sshf-no/project?pid=788403&amp;p_document_id=674134">Scandinavia</jats:ext-link> , along with an international umbrella group, <jats:underline>the</jats:underline> <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.gida-global.org/">Global Indigenous Data Alliance</jats:ext-link> <jats:underline>(GIDA)</jats:underline> . Together, these networks advocate for the rights of Indigenous Peoples over data that derive from them and that pertain to Nation membership, knowledge systems, customs, or territories. This lens on data sovereignty not only exceeds narrow notions of sovereignty as data localization and jurisdictional rights but also upends the assumption that the nation state is the legitimate locus of power. IDSov has thus become an important catalyst for broader conversations about what Indigenous sovereignty means in a digital world and how some measure of self-determination can be achieved under the weight of Big Tech dominance. </jats:p>

<jats:p>Photolyases, a ubiquitous class of flavoproteins, use blue light to repair DNA photolesions. In this work, we determined the structural mechanism of the photolyase-catalyzed repair of a cyclobutane pyrimidine dimer (CPD) lesion using time-resolved serial femtosecond crystallography (TR-SFX). We obtained 18 snapshots that show time-dependent changes in four reaction loci. We used these results to create a movie that depicts the repair of CPD lesions in the picosecond-to-nanosecond range, followed by the recovery of the enzymatic moieties involved in catalysis, completing the formation of the fully reduced enzyme-product complex at 500 nanoseconds. Finally, back-flip intermediates of the thymine bases to reanneal the DNA were captured at 25 to 200 microseconds. Our data cover the complete molecular mechanism of a photolyase and, importantly, its chemistry and enzymatic catalysis at work across a wide timescale and at atomic resolution.</jats:p>

<jats:p>It is clear that climate action is not on course either to achieve agreed-upon temperature goals or to protect people from increasingly severe climate impacts. The United Nations climate meeting (COP28) now underway is being called upon to provide a “course correction,” and the Global Stocktake (GST) to assess progress under the Paris Agreement has identified the need for “systems transformations.” As in previous years, COP28 will undoubtedly focus on finance and technology development and transfer, but these alone will not enable adequate, effective, and equitable climate action. It is time to expand focus to the third means of implementation: capacity building, without which a course correction involving multiple systems transformations is not going to occur.</jats:p>

<jats:p>Genes from second wild grass may have helped propel its success—but scientists don’t know how</jats:p>

<jats:p>AI-powered discovery could lead to revolutions in electronics, batteries, and solar cells</jats:p>