Catálogo de publicaciones - revistas

<jats:p>The fundamental processes of genetics have been captured with synthetic molecules.</jats:p>

<jats:p>Specific precursor states formed from soluble native proteins have been identified as leading to oligomerization and amyloid formation.</jats:p>

<jats:title>Going More Slowly</jats:title> <jats:p> Himalayan glaciers sometimes are called the “Third Pole” because of the amount of snow and ice they contain. Despite their importance as a global water reservoir and their essential role in Asian hydrology, how their mass is changing in response to global warming is not well known. <jats:bold> Bolch <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="310" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1215828">310</jats:related-article> ) review the contemporary evolution of glaciers in the Himalayan region, including those of the less well sampled region of the Karakoram to the Northwest, in order to provide a current, comprehensive picture of how they are changing. Most Himalayan glaciers are retreating at rates comparable to glaciers elsewhere in the world. In the Karakorum, on the other hand, advancing glaciers are more common. </jats:p>

<jats:title>A Specific Oxidative Catastrophe</jats:title> <jats:p> Three different classes of antibiotics induce bacterial cell death by the production of hydroxyl radicals. Hydroxyl radicals are powerful oxidizing agents in living cells and will oxidize the nucleic acid base, guanine, to form 8-oxoguanine, which is potentially mutagenic because it can pair with both cytosine and adenine and form lethal double-strand DNA breaks. <jats:bold> Foti <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="315" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1219192">315</jats:related-article> ) discovered that overproduction of the nucleotide sanitizer MutT, which hydrolyzes 8-oxo-dGTP to 8-oxo-dGMP, gives striking protection against cell death. </jats:p>

<jats:title>Hydrated in a Hurry</jats:title> <jats:p> Water has a major influence on the conformation of proteins and related biomolecules. However, so many water molecules participate in the hydrogen bonding networks that it can be difficult to pinpoint which specific interactions play the biggest role. <jats:bold> Nagornova <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="320" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1218709">320</jats:related-article> ) sought to answer this question for the case of a 10–amino acid ring—the antibiotic compound Gramicidin S—by probing the conformational impact of successive additions of one to 50 water molecules to the naked gas-phase structure. The primary changes in the overall ring geometry came from the addition of just the first two waters. </jats:p>

<jats:title>Bonded at the Source</jats:title> <jats:p> Asymmetric catalysis is a relatively mature field in the laboratory, with a diverse array of techniques available for the selective transformation of organic compounds. However, scaling up these techniques for industrial application remains challenging, in part because many catalysts act best on reagents that have been expensively modified, although this process often generates copious waste. <jats:bold> Zbieg <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="324" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1219274">324</jats:related-article> , published online 22 March) combat this challenge with a ruthenium-based catalyst that couples an unmodified bulk commodity feedstock (butadiene) with alcohols, forming carbon-carbon bonds to generate complex products with high selectivity. </jats:p>

<jats:title>A Sturdy Electrode Coating</jats:title> <jats:p> To operate efficiently, organic devices—such as light-emitting diodes—require electrodes that emit or take up electrons at low applied voltages (that is, have low work functions). Often these electrodes are metals, such as calcium, that are not stable in air or water vapor and have to be protected from environmental damage. <jats:bold> Zhou <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="327" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1218829">327</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6079" page="302" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1220829">Helander</jats:related-article> </jats:bold> ) report that a coating polymer containing aliphatic amine groups can lower the work functions of various types of electrodes by up to 1.7 electron volts and can be used in a variety of devices. </jats:p>

<jats:title>Upper Mantle Dislocations</jats:title> <jats:p> The driving forces behind plate tectonics act on a relatively weak upper mantle, such that the stress accumulated from colliding plates in the crust dissipates with depth. The physical properties of common mantle minerals, such as olivine, may be important in controlling mantle rheology, but they are difficult to measure directly. <jats:bold> Farla <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="332" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1218318">332</jats:related-article> ) monitored the deformation of randomly oriented olivine crystals at the pressures and temperatures of the upper mantle. Linear defects, known as dislocations, dissipated energy in samples that should normally be stable in several regions of the mantle, including below oceanic crust and around actively subducting slabs. Contrary to previous models, dislocations may dampen low-frequency seismic waves traveling through Earth's interior. </jats:p>

<jats:title>Old Plates and the Sea</jats:title> <jats:p> Estimates for the area and age of the ocean floor are at odds with assumptions for mantle convection, which imply that an older sea floor—rather than a new one—would be preferentially subducted over time. Previous efforts to explain these relationships have been based on geologic evidence and simple models. <jats:bold> Coltice <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="335" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1219120">335</jats:related-article> ) created numerical three-dimensional convection models representing more realistic physical boundaries, including a spherical Earth, the existence of continents and supercontinents over time, and realistic rheologies. A combination of continents and plate-like behavior of the ocean floor sufficed to produce the observed relationship between plate area and plate age, which explains why some old oceanic crust still remains. </jats:p>

<jats:title>Tic-Toc Segmentation Clock</jats:title> <jats:p> Molecular oscillators are an essential component of vertebrate segmentation, but whether they exist in segmented animals in general has been controversial for almost a decade. <jats:bold> Sarrazin <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="338" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1218256">338</jats:related-article> , published online 8 March; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6079" page="306" related-article-type="in-this-issue" vol="336" xlink:href="10.1126/science.1222242">Roth and Panfilio</jats:related-article> </jats:bold> ) demonstrate the existence of a segmentation clock in the growth zone of insects. Microsurgical manipulation and embryo culture revealed cyclic expression of the segmentation gene <jats:italic>Tc-odd</jats:italic> in the beetle <jats:italic>Tribolium castaneum</jats:italic> , which suggests that segmentation clocks are a widely shared mechanism that mediates animal segmentation. </jats:p>