Catálogo de publicaciones - revistas

<jats:title>Division Machinery Tagged</jats:title> <jats:p> An international consortium of labs has been testing the feasibility of large-scale screening for insights into the function of mammalian proteins by expressing a tagged version of proteins from bacterial artificial chromosomes harbored in mammalian cells. Depending on the tag used, <jats:bold> Hutchins <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="593" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1181348">593</jats:related-article> , published online 1 April) were able to monitor localization of tagged proteins by microscopy or to isolate interacting proteins and subsequently identify the binding partners by mass spectrometry. Applying the technology to proteins implicated in control of cell division revealed about 100 protein machines required for mitosis. </jats:p>

<jats:title>Dusty Quasars</jats:title> <jats:p> Quasars are energetic sources thought to be fueled by matter accreting onto black holes a billion times more massive than the Sun. Some quasars are difficult to detect because of surrounding clouds of gas and dust, so much so that this population of objects has remained elusive. Based on a compilation of x-ray, optical, and mid-infrared data, <jats:bold> Treister <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="600" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1184246">600</jats:related-article> , published online 25 March; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5978" page="576" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189695">Primack</jats:related-article> </jats:bold> ) show that the evolution of quasars across cosmic time occurs during mergers of gas-rich galaxies, with an obscured phase preceding an unobscured state by about 100 million years. Other objects have been detected in diverse wavebands, including ultraluminous infrared galaxies, which are known to be the product of similar gas-rich mergers of massive galaxies. </jats:p>

<jats:title>Approaching Lactate Inorganically</jats:title> <jats:p> Conversion of biomass to value-added chemical compounds currently relies in large part on fermentation. For full-scale displacement of petroleum as the chemical industry's primary feedstock, alternative conversion technologies will be necessary. <jats:bold> Holm <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="602" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183990">602</jats:related-article> ) have found that Lewis acidic zeolite derivatives suspended in methanol can catalyze the selective conversion of glucose, fructose, and sucrose sugars to methyl lactate, a versatile synthetic intermediate for commercial products. The catalysts were easily separated from product mixtures and proved robust over six reaction and regeneration cycles. </jats:p>

<jats:title>Hotspots on Venus</jats:title> <jats:p> The surface of Venus shows clear signs of volcanism, but are there active volcanoes on Venus today? The answer to this question will bear on our understanding of the planet's climate evolution and interior dynamics. Using surface thermal emissivity data returned by the Venus Express spacecraft, <jats:bold> Smrekar <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="605" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1186785">605</jats:related-article> , published online 8 April) looked at three hotspots on Venus. These places were identified by analogy with terrestrial hotspots like Hawaii, which are believed to overlie mantle plumes and to be the most likely sites for current volcanic activity. Lava flows at the three hotspots have anomalously high thermal emissions when compared with their surroundings. Low emissivity is generally interpreted as the result of surface alteration by the corrosive atmosphere of Venus. High emissivity implies that not much alteration took place and thus that the hotspots must represent recently active volcanoes younger than 2.5 million years. </jats:p>

<jats:title>A Dip in the Carbon Pool</jats:title> <jats:p> Before the diversity of animal life exploded in the Cambrian, Earth's carbon cycle was apparently strongly altered by multiple glaciation events across the globe. Carbon isotope signatures from rocks in Australia measured by <jats:bold> Swanson-Hysell <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="608" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1184508">608</jats:related-article> ) suggest that an organic carbon reservoir formed between two global glaciations, or “snowball Earth,” several hundred million years earlier than expected. Anoxic sulfate-limited waters, caused by increased river outputs from melting glaciers, may have prohibited bacterial respiration, allowing for the accumulation of organic carbon. As organic carbon levels dropped, CO <jats:sub>2</jats:sub> was released, allowing the atmosphere to warm, preventing further glaciations, and permitting the eventual accumulation of oxygen in the oceans that led to the Cambrian explosion. </jats:p>

<jats:title>Riding the Monsoon</jats:title> <jats:p> Most air transport from the troposphere to the stratosphere occurs in the tropics, but additional transport may occur in areas of strong upward convection. <jats:bold> Randel <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="611" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1182274">611</jats:related-article> , published online 25 March) report satellite measurements of atmospheric hydrogen cyanide over the region where the Asian summer monsoon occurs, which indicate that air is transported from the surface to deep within the stratosphere. This mechanism represents a pathway for pollutants to enter the global stratosphere, where they might affect ozone chemistry, aerosol characteristics, and radiative properties. </jats:p>

<jats:title>Learning to Work Together</jats:title> <jats:p> In group endeavors, there is often a tension between working for the greater good of the group as a whole versus working for one's own benefit. Sometimes these paths coincide and sometimes they do not; furthermore, the choices made by other group members can influence the calculation of which path to take. A pair of studies now approaches this challenge from experimental and theoretical points of view. In a forest or fishery, harvesting of wood or food needs to take into account the renewable character of the resource, as well as spatial heterogeneity. <jats:bold> Janssen <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="613" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183532">613</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="578" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189969"> <jats:bold>Putterman</jats:bold> </jats:related-article> ) show that communication among the group members is key, both to establishing a maintainable rate of harvesting, as well as enforcement via punishment of noncompliers. <jats:bold> Boyd <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="617" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183665">617</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="578" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189969"> <jats:bold>Putterman</jats:bold> </jats:related-article> ) develop a model showing that punishment, which is a costly activity, is most effectively levied when implemented with the approval of group members; that is, coordinated punishment works to the benefit of the whole, whereas individual actions do not. </jats:p>

<jats:title>Learning to Work Together</jats:title> <jats:p> In group endeavors, there is often a tension between working for the greater good of the group as a whole versus working for one's own benefit. Sometimes these paths coincide and sometimes they do not; furthermore, the choices made by other group members can influence the calculation of which path to take. A pair of studies now approaches this challenge from experimental and theoretical points of view. In a forest or fishery, harvesting of wood or food needs to take into account the renewable character of the resource, as well as spatial heterogeneity. <jats:bold> Janssen <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="613" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183532">613</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="578" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189969"> <jats:bold>Putterman</jats:bold> </jats:related-article> ) show that communication among the group members is key, both to establishing a maintainable rate of harvesting, as well as enforcement via punishment of noncompliers. <jats:bold> Boyd <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="617" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1183665">617</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="578" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1189969"> <jats:bold>Putterman</jats:bold> </jats:related-article> ) develop a model showing that punishment, which is a costly activity, is most effectively levied when implemented with the approval of group members; that is, coordinated punishment works to the benefit of the whole, whereas individual actions do not. </jats:p>

<jats:title>The Wasps and the Bees</jats:title> <jats:p> Sex development in bees and wasps depends on whether or not they develop from a haploid unfertilized egg (resulting in males) or diploid fertilized egg (resulting in females). Although these ploidy-level developmental processes are conserved among bees and wasps, the mechanisms that direct development down a male or female pathway differ significantly. By examining the sex-determining genes in the parasitoid wasp <jats:italic>Nasonia</jats:italic> , <jats:bold> Verhulst <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="620" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1185805">620</jats:related-article> ) have shown that a maternal messenger RNA (mRNA) is necessary to initiate the female pathway. The mRNA operates in combination with conserved maternal and paternal genes to produce females, which explains why females are diploids. In unfertilized eggs, maternal provisioning of the gene transcript is too low to initiate the female pathway. </jats:p>

<jats:title>Pink for Me, Green for You</jats:title> <jats:p> Aphids come in different colors, a critical issue when fate is a question of pigmentation: Red aphids tend to be consumed by ladybugs and green ones by parasitic wasps. Aphid color is determined by carotenoids, the same group of chemicals that make flamingos pink. But unlike flamingos, which have to eat colored food to stay pink, aphids make their own pigment. Carotenoids are vital to animals, not only because of their decorative possibilities but also for their oxidation-protective qualities as visual pigments and immune-system modulators. On sifting through an aphid genome, <jats:bold>Moran and Jarvik</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="624" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1187113">624</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="5978" page="574" related-article-type="in-this-issue" vol="328" xlink:href="10.1126/science.1190417">Fukatsu</jats:related-article> </jats:bold> ) discovered that the machinery for producing carotenoids has been acquired by an ancestral aphid in a lateral transfer event from a fungus. Although a spontaneous yellow mutant aphid was found that still possesses the sequence for biosynthesis of the red carotenoid pigment torulene, the sequence was discovered to have a single point mutation that puts a stop to turning red. </jats:p>