Catálogo de publicaciones - revistas

<jats:title>Copper's light touch forges C-N bonds</jats:title> <jats:p> Organic photochemistry has traditionally relied on excitation in the ultraviolet, where carbon-based compounds tend to absorb. Over the past decade, the field has undergone a renaissance as compounds that absorb visible light have proven to be versatile catalysts for organic reactions. For the most part, however, these catalysts have contained rare metals such as ruthenium or iridium. Kainz <jats:italic>et al.</jats:italic> now report a blue light-driven C-N bond-forming reaction catalyzed by Earth-abundant copper (see the Perspective by Greaney). Through coordination to a chiral ligand, the copper center couples alkyl chlorides to indoles and carbazoles with a high degree of enantioselectivity. </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="6274" page="681" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad8313">681</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6274" page="666" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aaf1071">666</jats:related-article> </jats:p>

<jats:title>Improving plant disease responses</jats:title> <jats:p> Disease resistance in plants depends on genes that allow them to recognize when they are infected by a pathogen so that they can mount a timely defense response. Unfortunately, pathogens can often overcome endogenous disease resistance genes by evolving new virulence strategies that escape detection. Kim <jats:italic>et al.</jats:italic> modified the pathogen recognition systems in the model plant <jats:italic>Arabidopsis thaliana</jats:italic> to widen its reach. The approach should enable the development of crops with more durable disease resistance and hence reduce pesticide use and increase crop yields. </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="6274" page="684" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad3436">684</jats:related-article> </jats:p>

<jats:title>Stacking to prolong valley lifetime</jats:title> <jats:p> In the material MoSe <jats:sub>2</jats:sub> , which, like graphene, has a two-dimensional honeycomb crystal lattice, the electronic structure has two “valleys.” Electrons can be distinguished by the valley they reside in, making them act as potential information carriers. However, electrons easily lose this information by scattering into the other valley. Rivera <jats:italic>et al.</jats:italic> placed single layers of MoSe <jats:sub>2</jats:sub> and WSe <jats:sub>2</jats:sub> on top of each other and shone circularly polarized light on the structure. The light caused excitons—pairs of electrons and holes—to form so that the hole and electron came from the same valley but different layers. The valley-specific character of such excitons persisted far longer than would be possible in a single layer of either material. </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="6274" page="688" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aac7820">688</jats:related-article> </jats:p>

<jats:title>Flexible power for flexible electronics</jats:title> <jats:p> A challenge for flexible electronics is to couple devices with power sources that are also flexible. Ideally, they could also be processed in a way that is compatible with current microfabrication technologies. Huang <jats:italic>et al.</jats:italic> deposited a relatively thick layer of TiC on top of an oxide-coated Si film. After chlorination, most, but importantly not all, of the TiC was converted into a porous carbon film that could be turned into an electrochemical capacitor. The carbon films were highly flexible, and the residual TiC acted as a stress buffer with the underlying Si film. The films could be separated from the Si to form free-floating films, with the TiC providing a support layer. </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="6274" page="691" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad3345">691</jats:related-article> </jats:p>

<jats:title> Warming making bigger CO <jats:sub>2</jats:sub> swings </jats:title> <jats:p> The combined effects of climate change and vegetation dynamics at high northern latitudes have amplified the seasonal variation of atmospheric CO <jats:sub>2</jats:sub> concentrations over the past half century. Forkel <jats:italic>et al.</jats:italic> combined observations and models to show that climate warming has caused the photosynthetic uptake of carbon to increase faster than its respiratory release from the terrestrial biosphere. This has increased the difference from summer to winter, as well as the latitudinal gradient. Because of the physiological limitations to carbon uptake by terrestrial vegetation, this negative feedback to warming in the boreal north and Arctic cannot continue indefinitely. </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="6274" page="696" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aac4971">696</jats:related-article> </jats:p>

<jats:title>By land or by sea</jats:title> <jats:p> How much of an effect does terrestrial groundwater storage have on sea-level rise? Reager <jats:italic>et al.</jats:italic> used gravity measurements made between 2002 and 2014 by NASA's Gravity Recovery And Climate Experiment (GRACE) satellites to quantify variations in groundwater storage. Combining those data with estimates of mass loss by glaciers revealed groundwater's impact on sea-level change. Net groundwater storage has been increasing, and the greatest regional changes, both positive and negative, are associated with climate-driven variability in precipitation. Thus, groundwater storage has slowed the rate of recent sea-level rise by roughly 15%. </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="6274" page="699" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad8386">699</jats:related-article> </jats:p>

<jats:title>Long-term partners uncoupled</jats:title> <jats:p> Methane-munching archaea in marine sediments live closely coupled to sulfate-reducing bacteria in a syntrophic relationship. Surprisingly, however, these archaea do not necessarily need their bacterial partners to survive or grow. Scheller <jats:italic>et al.</jats:italic> performed stable isotope incubation experiments with deep-sea methane seep sediments (see the Perspective by Rotaru and Thamdrup). Several groups of methane-oxidizing archaea could use a range of soluble electron acceptors instead of coupling to active bacterial sulfate reduction. This decoupled pathway shows that methane-oxidizing archaea transfer electrons extracellularly and may even possess the capacity to respire iron and manganese minerals that are abundant in seafloor sediments. </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="6274" page="703" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad7154">703</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6274" page="658" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aaf0741">658</jats:related-article> </jats:p>

<jats:title>Neuroendocrine cells as air sensors</jats:title> <jats:p> Liters of air pass through the lung every minute. Signals in the atmospheric environment are processed into physiological outputs, including the immune response. Branchfield <jats:italic>et al.</jats:italic> show that rare airway cells called pulmonary neuroendocrine cells (PNECs) sense and respond to airborne cues (see the Perspective by Whitsett and Morrisey). Inactivating <jats:italic>Roundabout</jats:italic> genes in mouse PNECs prevents normal PNEC clustering and causes an increase in the production of neuropeptides, which in turn trigger a heightened immune response. Thus PNECs, despite their rarity, are sensitive and effective rheostats on the airway wall that receive, interpret, and respond to environmental stimuli. </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="6274" page="707" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad7969">707</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6274" page="662" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aaf1429">662</jats:related-article> </jats:p>

<jats:title>T cells target peptide combos</jats:title> <jats:p> One of the enduring mysteries of autoimmunity is the identity of the specific proteins targeted by autoimmune T cells. Delong <jats:italic>et al.</jats:italic> used mass spectrometry to elucidate the peptide targets of autoimmune T cells isolated from a mouse model of type 1 diabetes. T cells targeted hybrid peptides formed by the covalent linking of a peptide derived from pro-insulin to other peptides derived from proteins found in pancreatic beta cells. T cells isolated from the pancreatic islets of two individuals with type 1 diabetes also recognized such hybrid peptides, suggesting that they may play an important role in driving disease. </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="6274" page="711" related-article-type="in-this-issue" vol="351" xlink:href="10.1126/science.aad2791">711</jats:related-article> </jats:p>