Catálogo de publicaciones - revistas

<jats:p> Ultrathin nickel coatings allow silicon to act as the oxygen-generating electrode in the direct formation of hydrogen from water with sunlight. <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="6160" page="836" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241327"> Kenney <jats:italic>et al.</jats:italic> </jats:related-article> ] </jats:named-content> </jats:p>

<jats:p> A family of transposable elements have played an important role in the evolution of dosage compensation in fruit flies. <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="6160" page="846" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1239552">Ellison and Bachtrog</jats:related-article> ] </jats:named-content> </jats:p>

<jats:p> Genome sequencing has defined the genetic basis for a primary immunodeficiency disease. <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="6160" page="866" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1243292"> Angulo <jats:italic>et al.</jats:italic> </jats:related-article> ] </jats:named-content> </jats:p>

<jats:p>Satellite and in situ sensor data complement long-term studies of individual lakes to provide insights into the effects of climate change and pollution.</jats:p>

<jats:title> The p <jats:italic>K</jats:italic> <jats:sub>a</jats:sub> of P450 </jats:title> <jats:p> Cytochrome P450 enzymes oxidize hydrocarbons through activation of oxygen at heme iron centers. However, the protein backbone has various sites (particularly tyrosine residues) that are also sensitive to oxidation, so how can the enzyme rapidly transform substrates without attacking itself? <jats:bold> Yosca <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="6160" page="825" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1244373">825</jats:related-article> ) explored the energetics of the competition between substrate and self-oxidation by measuring the p <jats:italic>K</jats:italic> <jats:sub>a</jats:sub> of the enzyme's iron(IV)hydroxide motif. Cysteine thiolate coordination to iron in the P450 structure raised the p <jats:italic>K</jats:italic> <jats:sub>a</jats:sub> almost to 12—rendering the iron oxo far more basic than analogous motifs in other heme environments. Correspondingly, the electronic environment for H-atom transfer from the substrate was relatively favorable, compared to electron transfer from a backbone residue. </jats:p>

<jats:title>Long-Lived Donors</jats:title> <jats:p> Quantum computing in materials such as silicon would simplify integration with existing electronic components; however, the coherence times of such qubits, especially at room temperature, are affected by the interaction with the busy environment of a solid. Eliminating isotopic impurities from the host material improves coherence times, as observed for qubits, based on the nuclear spin of neutral P donors in Si. <jats:bold> Saeedi <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="6160" page="830" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1239584">830</jats:related-article> ) modified this system by using charged P donors instead of neutral ones; by manipulating the states of the donors optically and using dynamical decoupling, the coherence time of the qubits was extended to 3 hours at cryogenic temperatures and 39 minutes at room temperature. </jats:p>

<jats:title>Monolayer Graphene via Two Transfers</jats:title> <jats:p> Oriented monolayers of graphene containing some bilayer regions can be formed on silicon carbide crystal surfaces, but, to be cost effective, the graphene needs to be exfoliated and transferred to other substrates so that the silicon carbide crystal can be reused. <jats:bold> Kim <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="6160" page="833" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1242988">833</jats:related-article> , published online 31 October) used a nickel film grown to a thickness designed to impart a particular surface stress as a “handle” to exfoliate the graphene layer for transfer to a silica substrate. An additional gold layer was then used to remove the excess monolayer from the bilayer regions to create a monolayer suitable for electronics applications. </jats:p>

<jats:title>Stabilizing Silicon</jats:title> <jats:p> Solar-driven water splitting has potential as an energy storage mechanism to supplement the direct conversion of sunlight to electricity. A submersed integrated device has been proposed both to absorb the light and to catalyze the reaction, but stability has been a problem. <jats:bold> Kenney <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="6160" page="836" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1241327">836</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article issue="6160" page="" related-article-type="in-this-issue" vol="342">Turner</jats:related-article> </jats:bold> ) found that a nickel coating, thin enough to let light through, could protect a silicon absorber in the alkaline environment of a lithium/potassium borate electrolyte. The nickel also functioned as the oxidation catalyst, and the lithium ions helped to establish a protective film structure in situ. </jats:p>

<jats:title>[2+2] Asymmetrically</jats:title> <jats:p> Catalysts in thermal reactions operate by lowering energy barriers of bound substrates, and thereby increasing the proportion of reagents that can proceed to products at a given temperature. In photochemical reactions, light provides the energy to surmount the barrier. It is therefore challenging to alter selectivity through catalysis, because the catalyst may not be bound when a given reagent absorbs the light. <jats:bold>Brimioulle and Bach</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6160" page="840" related-article-type="in-this-issue" vol="342" xlink:href="10.1126/science.1244809">840</jats:related-article> ) surmounted this problem in the light-induced intramolecular [2+2] cycloaddition of enones by using a catalyst that shifted the absorption wavelength of the bound substrate. The light was thus predominantly absorbed by substrate-catalyst complexes, enabling asymmetric induction by the catalyst to provide enantiomerically enriched products. </jats:p>