Catálogo de publicaciones - revistas

<jats:title>Imaging Hydrogen Bonds</jats:title> <jats:p> The decoration of atomic force microscope tips with terminal CO molecules has afforded much higher resolution of the bonding of adsorbed molecules. <jats:bold> Zhang <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="611" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242603">611</jats:related-article> , published online 26 September) show that this method, in combination with density function theory calculations, can image and characterize hydrogen-bonding contacts formed between 8-hydroxyquinoline molecules adsorbed on the (111) surface of copper under cryogenic conditions. At room temperature, a different bonding configuration was revealed that was the result of the molecules dehydrogenating on the copper surface and coordinating with surface copper atoms. </jats:p>

<jats:title>Better Contact Along the Edge</jats:title> <jats:p> Electrical contact to graphene is normally done with metal contacts on its flat face, where there are few strong bonding sites for the metal. <jats:bold> Wang <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="614" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1244358">614</jats:related-article> ) encapsulated graphene with hexagonal boron nitride sheets and made metal contacts along its edge, where bonding orbitals are exposed. The resulting heterostructures had high electronic performance, with room-temperature carrier mobilities near the theoretical phonon-scattering limit. </jats:p>

<jats:title>Deep Heating</jats:title> <jats:p> Global warming is popularly viewed only as an atmospheric process, when, as shown by marine temperature records covering the last several decades, most heat uptake occurs in the ocean. How did subsurface ocean temperatures vary during past warm and cold intervals? <jats:bold> Rosenthal <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="617" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1240837">617</jats:related-article> ) present a temperature record of western equatorial Pacific subsurface and intermediate water masses over the past 10,000 years that shows that heat content varied in step with both northern and southern high-latitude oceans. The findings support the view that the Holocene Thermal Maximum, the Medieval Warm Period, and the Little Ice Age were global events, and they provide a long-term perspective for evaluating the role of ocean heat content in various warming scenarios for the future. </jats:p>

<jats:title>Prairie Redux</jats:title> <jats:p> Tallgrass prairie is extinct across much of its former range in the midwestern United States, but relicts preserved in cemeteries and nature reserves allow functional comparison of former grassland soils with modern agricultural soils. <jats:bold> Fierer <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="621" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243768">621</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="565" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1244579"> <jats:bold>Scholes and Scholes</jats:bold> </jats:related-article> ) took matched soil samples from sites representing the gamut of climate conditions and modeled the combination of genomic analysis and environmental data to resurrect the historical prairie soil communities, identifying the nutrient-scavenging Verrucomicrobia as keystone bacteria in functioning prairie. </jats:p>

<jats:title>First Defense</jats:title> <jats:p> In defense against bacterial infection, plants carry a cell-surface receptor, known as FLS2, that can bind to a fragment of bacterial flagellin and trigger defense responses. <jats:bold> Y. Sun <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="624" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243825">624</jats:related-article> , published online 10 October) investigated the structural details that govern the binding between FLS2, its co-receptor BAK1, and the flagellin fragment flg22. The assembled complex initiates signals to activate the plant's innate immune response. </jats:p>

<jats:title>Chilly Repression Stalls Flowering</jats:title> <jats:p> In a cool spring, flowering might be delayed compared to a warm spring, even though the change in day length marches on regardless of temperature. <jats:bold> Lee <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="628" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241097">628</jats:related-article> , published online 12 September; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="566" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1245861">Nilsson</jats:related-article> </jats:bold> ) now show that this delay in flowering is a regulated process, not simply a consequence of sluggish metabolism. In the model plant <jats:italic>Arabidopsis</jats:italic> , transcription of the gene encoding the regulator SHORT VEGETATIVE PHASE (SVP) is unaffected by temperature, but the stability of the SVP protein is decreased at higher temperatures. Its regulatory partner, <jats:italic>FLOWERING LOCUS M</jats:italic> ( <jats:italic>FLM</jats:italic> )- <jats:italic>β</jats:italic> , is the product of alternative splicing of transcripts from the gene encoding FLM that favors the β form at lower temperatures. SVP and FLM-β form a complex that represses flowering. At lower temperatures, more of the repressive complex is present and flowering is delayed. At higher temperatures, SVP tends to degrade and FLM-β tends not to be produced, yielding reduced levels of the repressive complex, which allows flowering to proceed. </jats:p>

<jats:title>Not All Neurons Are Alike</jats:title> <jats:p> As life proceeds, many cells acquire individualized mutations. In the immune system, genome rearrangements generate useful antibody diversity. <jats:bold> McConnell <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="632" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243472">632</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="564" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1246942"> <jats:bold>Macosko and McCarroll</jats:bold> </jats:related-article> ) now show that human neurons also diversify. Neurons taken from postmortem human frontal cortex tissue and neurons derived from induced pluripotent stem cell differentiation in vitro showed surprising diversity in individual cell genomes. Up to 41% of the frontal cortex neurons had copy number variations—no two alike—with deletions more common than duplications. </jats:p>

<jats:title>The Good Scar</jats:title> <jats:p> We tend to think of scars as bad and, in the central nervous system, as counterproductive to recovery. Studying mice, <jats:bold> Sabelström <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6158" page="637" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242576">637</jats:related-article> ) prevented resident stem cells from proliferating after spinal cord injury. Without the astrocytes generated by the neural stem cells, recovery from spinal cord lesions was poorer than normal. Thus, somewhat counterintuitively, glial scarring appears to limit spinal cord damage and support the remaining cells. </jats:p>

<jats:p>Listen to stories on neural correlates for music and speech learning, understanding the role of scars in spinal cord injury, deep-brain stimulation for depression, and more.</jats:p>

<jats:p>Genetic variations in genes that metabolize and transport drugs in the body are known to affect the therapeutic response in different individuals by altering the absorption, distribution, metabolism, or elimination (ADME) of those drugs. Preemptively assessing multiple pharmacogenetic factors holds tremendous potential to improve treatment by understanding the effect of important genetic variants in advance, rather than waiting to test a patient for genetic markers for each individual drug at the time of prescription. Higher throughput and more comprehensive clinical genetic testing is now available, allowing clinical testing to expand from a single gene to comprehensive panels of relevant genes—a more attractive and cost-effective approach. Preemptive clinical testing for pharmacogenetic genes has been implemented in a pediatric setting. This approach has great advantages for both the patient and the physician. However, careful consideration with regard to medical data management and communication with patients and health care providers is necessary.</jats:p>