Catálogo de publicaciones - revistas

<jats:title>Actin cortex controls cell migration</jats:title> <jats:p> Cell migration is mainly controlled by local actin polymerization–driven membrane protrusion. However, a second structural mechanism might also regulate membrane protrusions and directed migration: changes in the density of the attachment between the plasma membrane and the underlying F-actin cortex, a parameter related to membrane tension. Many types of attachment and signaling mechanisms are known to alter the density of membrane-proximal cortical actin. Bisaria <jats:italic>et al.</jats:italic> designed a membrane-proximal F-actin (MPA) reporter that could directly measure local changes in the density of MPA in living cells. Levels of MPA were surprisingly low toward the front of migrating cells despite an opposing high overall concentration of F-actin in the same front region. The researchers propose that MPA density can integrate different signaling processes to direct local membrane protrusions and stabilize cell polarity during cell migration. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1205" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aay7794">1205</jats:related-article> </jats:p>

<jats:title>Drug inhibition of glycosyltransferases</jats:title> <jats:p> Mycobacteria, including the species that causes tuberculosis (TB), synthesize a complex cell wall that helps to support and protect the bacterial cells. The major components of the cell wall include complex heteropolysaccharides that are synthesized in the periplasmic space. Zhang <jats:italic>et al.</jats:italic> determined the cryo–electron microscopy structures of two transmembrane glycosyltransferase enzyme complexes that use a lipid-anchored sugar donor to append arabinose units to the cell wall polysaccharides. They also captured the anti-TB drug ethambutol bound within these complexes and observed that it binds in a site overlapping both donor and acceptor sugars. Mapping of resistance mutants provides a structural understanding of how resistance emerges while preserving function of the enzyme and may help to guide the development of next-generation anti-TB drugs that target these enzymes. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1211" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aba9102">1211</jats:related-article> </jats:p>

<jats:title>Light under compression</jats:title> <jats:p> The ability to confine light to volumes much smaller than the wavelength produces high electromagnetic fields that can then be exploited in chemical and biological sensing and detection applications. Using silver nanocubes placed on a graphene surface, Epstein <jats:italic>et al.</jats:italic> developed a single, nanometer-scale acoustic graphene plasmon cavity device that can confine mid-infrared and terahertz radiation with mode volume confinement factors of 5 × 10 <jats:sup>–10</jats:sup> . With the response being dependent on the size of the nanocube and electrically tunable, the results demonstrate a powerful platform with which to develop sensors in what has been a challenging wavelength regime where molecular fingerprints reside. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1219" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb1570">1219</jats:related-article> </jats:p>

<jats:title>Sequencing for seismic structures</jats:title> <jats:p> Structures illuminated by seismic waves at the core-mantle boundary of the Earth are traditionally found by focusing on a specific target area. Kim <jats:italic>et al.</jats:italic> used an unsupervised manifold learning algorithm called “the Sequencer” to automatically detect anomalies in seismic data (see the Perspective by Miller). Using this technique, they uncovered structures at the core-mantle boundary across the entire Pacific region all at once. They found many structures previously identified, but also a new, ultra-low-velocity zone beneath the Marquesas Islands. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1223" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aba8972">1223</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1183" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abc3134">1183</jats:related-article> </jats:p>

<jats:title>Charging into epoxides</jats:title> <jats:p> Ethylene oxide is a strained, reactive molecule produced on a vast scale as a plastics precursor. The current method of synthesis involves the direct reaction of ethylene and oxygen at high temperature, but the original protocol relied on the reduction of chlorine to produce a chlorohydrin intermediate. Leow <jats:italic>et al.</jats:italic> report a room temperature method that returns to the chlorine route but uses electrochemistry to generate it catalytically from chloride (see the Perspective by Barton). This efficient process uses water in place of oxygen and can be integrated with the electrochemical generation of ethylene from carbon dioxide. Propylene oxide can be produced using the same method. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1228" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz8459">1228</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1181" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb8061">1181</jats:related-article> </jats:p>

<jats:title>Coherent electronic waves</jats:title> <jats:p> The wave nature of conducting electrons in solids can be revealed through interference effects. In layered materials, these effects are most often seen in in-plane transport. By contrast, Putzke <jats:italic>et al.</jats:italic> studied electronic transport perpendicular to the conductive layers in the ultraclean delafossites PdCoO <jats:sub>2</jats:sub> and PtCoO <jats:sub>2</jats:sub> . When an in-plane magnetic field was applied, the electrical resistance exhibited periodic oscillations as a function of field magnitude. The findings can be explained through a model that requires that the electronic waves remain coherent over macroscopic distances. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1234" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aay8413">1234</jats:related-article> </jats:p>

<jats:title>Taking stock of our losses</jats:title> <jats:p> Earth's ice sheets are melting and sea levels are rising, so it behooves us to understand better which climate processes are responsible for how much of the mass loss. Smith <jats:italic>et al.</jats:italic> estimated grounded and floating ice mass change for the Greenland and Antarctic ice sheets from 2003 to 2019 using satellite laser altimetry data from NASA's ICESat and ICESat-2 satellites. They show how changing ice flow, melting, and precipitation affect different regions of ice and estimate that grounded-ice loss averaged close to 320 gigatons per year over that period and contributed 14 millimeters to sea level rise. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1239" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz5845">1239</jats:related-article> </jats:p>

<jats:title>The benefits of ecosystem restoration</jats:title> <jats:p> Human activities have fundamentally altered many ecosystems. Recent successful restoration efforts have led to healthier ecosystems, but this has led to a disruption in economies dependent on the altered state of the system. One of the best-known trophic cascades is the sea otter–kelp forest system, wherein recovery of once extirpated sea otters is bringing back biodiverse and healthy kelp forests but reducing the abundance of harvested shellfish. Gregr <jats:italic>et al.</jats:italic> looked at the costs and benefits of this shift and found that for key trade-offs, the value of kelp forest–associated features such as tourism, fin fish fisheries, and carbon capture outweighed the losses to economies (see the Perspective by Estes and Carswell). Thus, ecosystem recovery can benefit both ecosystems and economies. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1243" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aay5342">1243</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1178" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abc7060">1178</jats:related-article> </jats:p>

<jats:title>Ten rings on one axle</jats:title> <jats:p> Rotaxanes consist of molecular rings threaded on a central axle. Most approaches to their synthesis have focused on introducing a single ring per axle. Qiu <jats:italic>et al.</jats:italic> now report a systematic approach to threading up to 10 adjacent rings consecutively. The axle's end groups were constructed to attract free-floating rings when reduced and then to push those rings toward the center upon oxidation. Products of each successive reduction-oxidation cycle were characterized by nuclear magnetic resonance spectroscopy and mass spectrometry. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6496" page="1247" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb3962">1247</jats:related-article> </jats:p>