Catálogo de publicaciones - revistas

<jats:title>Scattering neutrons asymmetrically</jats:title> <jats:p> The crystal structure of solid materials often influences their properties. The more symmetric the structure, the less dependent these properties are on the spatial direction. The superconductors that derive from the compound BaFe <jats:sub>2</jats:sub> As <jats:sub>2</jats:sub> are an exception: Their electronic transport properties can be anisotropic even in the phase where the crystal is symmetric. By scattering neutrons off their samples, Lu <jats:italic>et al.</jats:italic> found that the magnetic properties of these materials can also be anisotropic. The similar temperature and doping dependence of the anisotropies of both transport and magnetic properties suggests that they may have a common cause. </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="6197" page="657" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1251853">657</jats:related-article> </jats:p>

<jats:title>You only see what you want to see</jats:title> <jats:p> We often focus on a particular item out of a thousand objects in a visual scene. This ability is called selective attention. Selective attention enhances the responses of sensory nerve cells to whatever is being observed and dampens responses to any distractions. Zhang <jats:italic>et al.</jats:italic> identified a region of the mouse forebrain that modulates responses in the visual cortex. This modulation improved the mouse's performance in a visual task. </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="6197" page="660" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1254126">660</jats:related-article> </jats:p>

<jats:p> Climate warming is expected to reduce oxygen (O <jats:sub>2</jats:sub> ) supply to the ocean and expand its oxygen minimum zones (OMZs). We reconstructed variations in the extent of North Pacific anoxia since 1850 using a geochemical proxy for denitrification (δ <jats:sup>15</jats:sup> N) from multiple sediment cores. Increasing δ <jats:sup>15</jats:sup> N since ~1990 records an expansion of anoxia, consistent with observed O <jats:sub>2</jats:sub> trends. However, this was preceded by a longer declining δ <jats:sup>15</jats:sup> N trend that implies that the anoxic zone was shrinking for most of the 20th century. Both periods can be explained by changes in winds over the tropical Pacific that drive upwelling, biological productivity, and O <jats:sub>2</jats:sub> demand within the OMZ. If equatorial Pacific winds resume their predicted weakening trend, the ocean’s largest anoxic zone will contract despite a global O <jats:sub>2</jats:sub> decline. </jats:p>

<jats:title>Modeling computer chips on real brains</jats:title> <jats:p> Computers are nowhere near as versatile as our own brains. Merolla <jats:italic>et al.</jats:italic> applied our present knowledge of the structure and function of the brain to design a new computer chip that uses the same wiring rules and architecture. The flexible, scalable chip operated efficiently in real time, while using very little power. </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="6197" page="668" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1254642">668</jats:related-article> </jats:p>

<jats:title>Microbial life thrives in an oily bubble</jats:title> <jats:p> Microorganisms can break down hydrocarbons in oil reservoirs. Microbes grow primarily at the interface between oil and water, where they can find nutrients and dispose of metabolites. Meckenstock <jats:italic>et al.</jats:italic> now show that tiny water droplets can also provide a suitable home for hydrocarbon-degrading microorganisms. The authors examined oil from Pitch Lake, Trinidad and Tobago, and found that diverse microorganisms thrived in these tiny isolated microhabitats. </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="6197" page="673" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1252215">673</jats:related-article> </jats:p>

<jats:title>How microbes compete for nitrate</jats:title> <jats:p> Much of the ammonia fertilizer we use ends up in surface or coastal waters as nitrate. This runoff lowers water quality and damages ecosystems. Although microbial nitrogen respiration influences the fate of nitrate, it is unclear which environmental factors exert the most control. Kraft <jats:italic>et al.</jats:italic> performed multiple long-term incubation studies of microbial communities from marine sediments. The relative supply of nitrate and nitrite, as well as total carbon and nitrogen, provided selective pressures that drove communities toward denitrification or ammonification. The average generation time of the community also strongly influenced which respiration pathway dominated. </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="6197" page="676" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1254070">676</jats:related-article> </jats:p>

<jats:title>Bad cholesterol: Bad for bacteria, too?</jats:title> <jats:p> Why do viral infections, such as the common cold, leave people more susceptible to bacterial pneumonia? One reason is that type I interferons, secreted proteins that initiate antiviral immune responses, suppress other inflammatory molecules that protect against bacterial infection. Reboldi <jats:italic>et al.</jats:italic> investigated how this suppression occurs on a molecular level in mice. Interferons stimulated expression of a particular enzyme that catalyzes the production of the oxysterol 25-hydroxycholesterol (25-HC). 25-HC inhibits the function of the transcription factor SREBP, which normally drives expression of the gene that encodes interleukin-1, a secreted inflammatory protein with wide-ranging antibacterial functions. </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="6197" page="679" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1254790">679</jats:related-article> </jats:p>

<jats:title>Better blood thinner, without bleeding</jats:title> <jats:p> Blood thinners prevent heart attacks and strokes by making it harder for blood to clot, but these drugs can put patients at risk of dangerous bleeding. Now Moeckle <jats:italic>et al.</jats:italic> describe an enzyme that can prevent clots without this perilous side effect. They engineered the enzyme apyrase to remove the pro-clotting molecule ADP from the blood quickly. In dogs and mice with heart attacks, apyrase stopped blood cells from aggregating, the first step in forming a clot. At the highest dose, the animals suffered less heart damage and did not bleed excessively. In comparison, clopidogrel, a blood thinner used currently in patients, protected the heart less well and did cause excessive bleeding. </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="6197" page="684" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1253525">684</jats:related-article> </jats:p>

<jats:title>Drugs that provide the splice of life</jats:title> <jats:p> Motor neurons relay signals from the nervous system to muscle fibers. In patients with spinal muscular atrophy, a protein required for the survival of these neurons is deficient or missing altogether, so the neurons gradually die and the patients' muscles waste away. The disease is currently untreatable. Naryshkin <jats:italic>et al.</jats:italic> discovered small-molecule drugs that cause cells to produce the missing protein by altering how a specific mRNA is put together, or “spliced” (see the Perspective by Vigevani and Valcárcel). When the researchers used the drugs to treat diseased mice, the mice showed marked improvement in muscle mass, motor function, and survival. </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="6197" page="688" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1250127">688</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6197" page="624" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1258444">624</jats:related-article> </jats:p>

<jats:title>Bending the benefits of polyunsaturates</jats:title> <jats:p> We have often heard that it is beneficial to eat polyunsaturated fatty acids. We also know that some organelles such as synaptic vesicles are extremely rich in polyunsaturated lipids. However, what polyunsaturated lipids do in our body is unclear. Using cell biology, biochemical reconstitutions, and molecular dynamics, Pinot <jats:italic>et al.</jats:italic> show that polyunsaturated phospholipids can change the response of membranes to proteins involved in membrane curvature sensing, membrane shaping, and membrane fission. Polyunsaturated phospholipids make the plasma membrane more amenable to deformation; facilitate endocytosis; and, in reconstitution experiments, increased membrane fission by the dynamin-endophilin complex. </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="6197" page="693" related-article-type="in-this-issue" vol="345" xlink:href="10.1126/science.1255288">693</jats:related-article> </jats:p>