Catálogo de publicaciones - revistas

<jats:title>How to hide a dimension from view</jats:title> <jats:p> Compacted dimensions are essential ingredients of advanced string theories; the extra dimensions used to describe the world are hidden from view, or compacted. Pendry <jats:italic>et al.</jats:italic> used concepts of transformation optics, in which metamaterials are designed to produce specific optical properties, to show theoretically that compacted dimensions could be possible in plasmonic structures. For example, simulations with a metallic grating and periodically doped graphene revealed that two-dimensional structures exhibit optical properties of a bulk material. To all intents and purposes, it looks as if one of the dimensions is compacted. The results could have practical application in designing broadband optical absorbers. </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="6365" page="915" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aap7939">915</jats:related-article> </jats:p>

<jats:title>Hydrogen from methane in molten metal</jats:title> <jats:p> The hydrogen used in making ammonia and other industrial reactions is produced mainly through steam reformation of methane over nickel catalysts. This high-temperature process also releases carbon dioxide, a greenhouse gas. Upham <jats:italic>et al.</jats:italic> used nickel dissolved in molten bismuth to pyrolyze methane to release hydrogen and form carbon, which floats to the surface of the melt, where it can be removed. Carbon formation on steam-reforming catalysts is usually a deactivating side reaction, but in the new process, the carbon can be stored or incorporated into composite materials. </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="6365" page="917" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aao5023">917</jats:related-article> </jats:p>

<jats:title>Tracking a trio of rubidium atoms</jats:title> <jats:p> Crossed molecular beams have provided decades' worth of knowledge into how quantum mechanics governs chemical reactivity. Nonetheless, the technique is generally limited to the collision of two partners. Wolf <jats:italic>et al.</jats:italic> report on a three-body process with full quantum state resolution. By cooling rubidium atoms to ultralow temperatures in an optical trap, they were able to observe dimer formation, stabilized by collision with a third atom, and extract the precise dependence of product states on the initial states of the atoms involved. </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="6365" page="921" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aan8721">921</jats:related-article> </jats:p>

<jats:title>How the snapdragon chooses its color</jats:title> <jats:p> In some snapdragons, a yellow spot in a field of magenta shows the bee the best place to go. Flowers of a related subspecies are mainly yellow with magenta veins marking the target. Bradley <jats:italic>et al.</jats:italic> analyzed a locus that regulates the pattern of color. The locus contains an inverted gene duplication that encodes small RNAs that repress pigment biosynthesis. Analysis of flowers derived from a region of the Pyrenees where the subspecies coexist indicates that natural selection is operating upon the locus. </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="6365" page="925" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aao3526">925</jats:related-article> </jats:p>

<jats:title>Too much or too little—better than some</jats:title> <jats:p> Dengue fever is caused by a mosquito-transmitted flavivirus resembling Zika virus. Both viruses can cause severe diseases in humans with catastrophic sequelae. It has been suspected in humans, and shown in animal models, that the host's immune responses can make disease worse. Katzelnick <jats:italic>et al.</jats:italic> examined data from a long-term study of Nicaraguan children exposed to dengue virus (see the Perspective by Feinberg and Ahmed). They confirmed that antibody-dependent enhancement of disease occurs at a specific range of antibody concentrations. Low levels of antibody did not enhance disease, intermediate levels exacerbated disease, and high antibody titers protected against severe disease. These findings have major implications for vaccines against flaviviruses. Indeed, recent vaccine trials have shown evidence of severe disease in some recipients who were previously exposed to virus. </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="6365" page="929" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aan6836">929</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6365" page="865" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aaq0215">865</jats:related-article> </jats:p>

<jats:title>Mutation for microcephaly</jats:title> <jats:p> Zika virus infections in humans have been known since 1947. Microcephaly and neuropathologies associated with Zika have only been reported recently, most prevalently in the Americas. Yuan <jats:italic>et al.</jats:italic> investigated recent stable mutations in the virus genome and engineered them into a low-virulence ancestral strain (see the Perspective by Screaton and Mongkolsapaya). A single amino acid substitution (serine to asparagine, S139N) in the viral precursor membrane protein exacerbated symptoms in pregnant mice. The reverse mutation (N139S) was less virulent. The S139N mutation arose in 2013 in French Polynesia before the virus jumped to Brazil in 2015. In vitro, this amino acid change made the virus more infectious for mouse and human neural progenitor cells and promoted apoptosis. The terrible sequelae of infection during pregnancy could thus be the result of a simple viral mutation. </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="6365" page="933" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aam7120">933</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6365" page="863" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aaq1297">863</jats:related-article> </jats:p>

<jats:title>How protons power rotation</jats:title> <jats:p> Synthesis of adenosine triphosphate (ATP) in mitochondria is accomplished by a large molecular machine, the F <jats:sub>1</jats:sub> F <jats:sub>O</jats:sub> ATP synthase. Proton translocation across the F <jats:sub>O</jats:sub> region that spans the mitochondrial inner membrane drives ATP synthesis in the F <jats:sub>1</jats:sub> region through a rotational mechanism. Guo <jats:italic>et al.</jats:italic> present a high-resolution structure of the dimeric F <jats:sub>O</jats:sub> complex from <jats:italic>Saccharomyces cerevisiae</jats:italic> , determined by electron microscopy. The structure gives insights into how proton translocation powers rotation and suggests how F <jats:sub>O</jats:sub> dimers bend the membrane to give mitochondria their characteristic cristae. </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="6365" page="936" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aao4815">936</jats:related-article> </jats:p>

<jats:title>Cancer cells put ammonia back to work</jats:title> <jats:p> Ammonia, often considered a metabolic waste product, can be recycled to build new amino acids. Rapidly proliferating cells produce extracellular nitrogen. Spinelli <jats:italic>et al.</jats:italic> used metabolic tracing of <jats:sup>15</jats:sup> N to follow the fate of extracellular ammonia and its incorporation into more than 200 components of the nitrogen metabolome (see the Perspective by Dang). Accumulation of ammonia enabled glutamate dehydrogenase to function in reductive amination, which allowed incorporation of nitrogen from ammonia back into amino acids. Experiments in mice also showed incorporation of ammonia into glutamate, aspartate, and proline. </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="6365" page="941" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aam9305">941</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6365" page="862" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aaq1070">862</jats:related-article> </jats:p>

<jats:title>Structural basis for transcription activation</jats:title> <jats:p> Bacteria can initiate transcription through two independent classes of recruitment mechanisms. Liu <jats:italic>et al.</jats:italic> determined the cryo-electron microscopy structure of an intact class I transcription activation complex. The positions and orientations of all the components and the detailed protein-protein and protein-nucleic acid interactions reveal how an activator interacts with the promoter DNA and recruits RNA polymerase through the class I mechanism. Together with a recently reported class II transcription activation complex, the findings complete our structural understanding of bacterial transcription activation. </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="6365" page="947" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aao1923">947</jats:related-article> </jats:p>

<jats:title>Genetics of the passenger pigeon</jats:title> <jats:p> The now-extinct passenger pigeon used to be one of the most numerous vertebrates on Earth. Murray <jats:italic>et al.</jats:italic> examined the genomes of four passenger pigeon samples from different locales within its range. They describe the interplay between passenger pigeon population size, genome structure and recombination, and natural selection. They conclude that a reduction in genetic diversity provided few avenues for the bird to respond to human pressures, which ultimately drove it to extinction. </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="6365" page="951" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aao0960">951</jats:related-article> </jats:p>