Catálogo de publicaciones - revistas

<jats:p> A newly discovered population of neurons called island cells may be important signaling hubs within neural microcircuits for memory. <jats:named-content content-type="related-content"> [Also see Reports by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="891" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1243028"> Ray <jats:italic>et al.</jats:italic> </jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="896" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1244634"> Kitamura <jats:italic>et al.</jats:italic> </jats:related-article> ] </jats:named-content> </jats:p>

<jats:p> Cellular extensions called cytonemes may allow nonneuronal cells to communicate directly with each other over long distances. <jats:named-content content-type="related-content"> [Also see Research Article by <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/content/343/6173/1244624.full"> Roy <jats:italic>et al.</jats:italic> </jats:ext-link> ] </jats:named-content> </jats:p>

<jats:p> The structure of a flavirirus nonstructural protein provides mechanistic understanding for many of its functions. <jats:named-content content-type="related-content"> [Also see Report by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="881" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1247749"> Akey <jats:italic>et al.</jats:italic> </jats:related-article> ] </jats:named-content> </jats:p>

<jats:p> A rhodium-catalyzed reaction places a silicon substituent on the site farthest away from the largest group present on an aromatic ring. <jats:named-content content-type="related-content"> [Also see Research Article by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="853" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1248042">Cheng and Hartwig</jats:related-article> ] </jats:named-content> </jats:p>

<jats:title>Silicon Siting</jats:title> <jats:p> The synthesis of many pharmaceutical and agrochemical compounds requires selective functionalization of multiple different sites on aromatic ring frameworks. The size and electronic properties of the first substituent added can influence where the next one is likely to end up. <jats:bold>Cheng and Hartwig</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="853" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1248042">853</jats:related-article> , see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="850" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1250335"> <jats:bold>Tobisu and Chatani</jats:bold> </jats:related-article> ) discovered a rhodium-catalyzed reaction that is particularly sensitive to size that places a silicon substituent as far away as possible from the largest group already on the ring. The silicon group can then be replaced with carbon, oxygen, nitrogen, or halide substituents as needed. </jats:p>

<jats:title>Fear, Memory, and Place</jats:title> <jats:p> Contextual fear conditioning (CFC) is widely used as a hippocampal-dependent classical conditioning task to model human episodic memory. <jats:bold> Lovett-Barron <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="6173" page="857" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1247485">857</jats:related-article> ) combined in vivo imaging with pharmacology, pharmacogenetics, and optogenetics and they found that somatostatin-expressing, dendrite-targeting γ-aminobutyric acid–releasing interneurons in hippocampal area CA1 are required for CFC. During CFC, sensory features of the aversive event reach hippocampal output neurons through excitatory cortical afferents and require active inhibitory filtering to ensure that the hippocampus exclusively encodes the conditioned stimulus. </jats:p>

<jats:title>A 3D Graphene?</jats:title> <jats:p> Discoveries of materials with exciting electronic properties have propelled condensed matter physics over the past decade. Two of the best-known examples, graphene and topological insulators, have something in common: a linear energy-momentum relationship—the Dirac dispersion—in their two-dimensional (2D) electronic states. Topological insulators also have a more mundane aspect of their electronic structure, characterized by a band gap. Another class of materials, topological Dirac semimetals, has been proposed that has a linear dispersion along all three momentum directions—a bulk Dirac cone; these materials are predicted to have intriguing electronic properties and to be related to other exotic states through quantum phase transitions. <jats:bold> Liu <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="6173" page="864" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1245085">864</jats:related-article> , published online 16 January) detected such a state in the compound Na3Bi by using photoemission spectroscopy. </jats:p>

<jats:title>Toward an Artificial Muscle</jats:title> <jats:p> In designing materials for artificial muscles, the goals are to find those that will combine high strokes, high efficiency, long cycle life, low hysteresis, and low cost. Now, <jats:bold> Haines <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="6173" page="868" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1246906">868</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="845" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1250471"> <jats:bold>Yuan and Poulin</jats:bold> </jats:related-article> ) show that this is possible. Twisting high-strength, readily available polymer fibers, such as those used for fishing lines or sewing thread, to the point where they coil up, allowed construction of highly efficient actuators that could be triggered by a number of stimuli. </jats:p>

<jats:title>Optimizing Injectable Hydrogels</jats:title> <jats:p> Injectable hydrogels are showing promise as scaffolds in regenerative medicine because they can be injected in liquid form and transform in situ into the gel state. However, when exposed to ionic solutions, such as those found in the body, hydrogels can increase in volume by a factor of 2, which can weaken the material. <jats:bold> Kamata <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="6173" page="873" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1247811">873</jats:related-article> ) added a thermoresponsive component to a hydrogel so that the thermoresponsive component would tend to collapse in shape when heated and counteract the hydrogel's tendency to swell. Indeed, the resulting gel retained its unswollen volume following immersion in a physiological solution and retained its mechanical strength during repeated stretching or compression. </jats:p>

<jats:title>Robust to Change</jats:title> <jats:p> The variation in genetic sequences determining the binding of transcription factors is believed to be an important facet of evolution. However, the degree to which a genome is robust, that is, able to withstand changes and how robustness affects evolution is unclear. <jats:bold>Payne and Wagner</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6173" page="875" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1249046">875</jats:related-article> ) investigated the empirical support for mutational robustness by examining transcription factor (TF) binding in the mouse and yeast genomes. A network analysis of the degree of variation revealed that the sites with the highest affinity for TF binding exhibit the greatest tolerance for nucleotide substitutions, whereas low-affinity sites exhibit greater sensitivity to mutation. Thus, while mutational robustness and evolvability are antagonistic at the genotypic level, they are synergistic at the phenotypic level. </jats:p>