Catálogo de publicaciones - revistas

<jats:p>Analysis of microbial interactions in the wild shows that microbes cooperate to resist competition.</jats:p>

<jats:p>Cells have developed ways to sense and control the size of their organelles. Size-sensing mechanisms range from direct measurements provided by dedicated reporters to indirect functional readouts, and they are used to modify organelle size under both normal and stress conditions. Organelle size can also be controlled in the absence of an identifiable size sensor. Studies on flagella have dissected principles of size sensing and control, and it will be exciting to see how these principles apply to other organelles.</jats:p>

<jats:title>Predictions of Genetic Disease</jats:title> <jats:p> Many genome-wide association studies (GWAS) have identified loci and variants associated with disease, but the ability to predict disease on the basis of these genetic variants remains small. <jats:bold> Maurano <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="1190" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1222794">1190</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="6099" page="1179" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1227739">Schadt and Chang</jats:related-article> </jats:bold> ; see the cover) characterize the location of GWAS variants in the genome with respect to their proximity to regulatory DNA [marked by deoxyribonuclease I (DNase I) hypersensitive sites] by tissue type, disease, and enrichments in physiologically relevant transcription factor binding sites and networks. They found many noncoding disease associations in regulatory DNA, indicating tissue and developmental-specific regulatory roles for many common genetic variants and thus enabling links to be made between gene regulation and adult-onset disease. </jats:p>

<jats:title>Skipping the Odds</jats:title> <jats:p> When confined to a plane and placed in a magnetic field at low temperatures, electrons are separated by energy into the so-called Landau levels; adding an extra electron after a Landau level that has been filled is costly. In some systems, electron-electron interactions cause the appearance of sublevels, in a phenomenon known as the fractional quantum Hall effect (FQHE). This effect has been observed in graphene, but the number of levels that had been resolved was limited. <jats:bold> Feldman <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="1196" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1224784">1196</jats:related-article> ) directly measured the change in the chemical potential caused by varying electron density, which is controlled by gate voltage. Once the FQH states were identified, the Landau levels with odd-numerator fractional fillings were found to be missing between filling factors 1 and 2, because of the broken and preserved symmetries of graphene. These observations help to explain how the FQHE in graphene is different from that observed in conventional semiconductors, and the technique will also allow local measurements to be made; hence, monitoring of spatial variations in sample behavior is possible. </jats:p>

<jats:title>Iron Hopping</jats:title> <jats:p> Iron oxide minerals shuttle electrons around in a wide range of biogeochemical processes. <jats:bold> Katz <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="1200" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1223598">1200</jats:related-article> ) used time-resolved x-ray absorption spectroscopy to take a closer look at how this happens. By using photoionized surface dyes to inject electrons into three different solid oxide phases, they found that electrons hop among iron centers at rates that depend more on structure in their immediate vicinity than on the extended ordering of the crystal lattice. These observations bolster the prevailing small polaron model in which charge carriers associate closely with individual metal sites. </jats:p>

<jats:title>Enols in the Atmosphere?</jats:title> <jats:p> Keto/enol tautomerization (HC−C=O→C=C−OH) plays a central role in the chemistry of carbonyl compounds in a solution in which solvent and catalytic acids or bases can facilitate the proton transfer from C to O and back again. In contrast, analyses of atmospheric chemistry tend to exclude enol structure, on the assumption that tautomerization does not proceed regularly in gas phase. <jats:bold> Andrews <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="1203" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220712">1203</jats:related-article> , published online 16 August) used isotopic labeling to probe the photoisomerization pathway of gaseous acetaldehyde in the lab and discovered evidence for an enol. Subsequent modeling indicates that photogenerated enols could build up sufficiently in the troposphere to account for previously puzzling observations of organic acids in the atmosphere. </jats:p>

<jats:title>Pinning Down Nuclear Shells</jats:title> <jats:p> The nuclei of heavy atoms are destabilized by proton repulsions, and, conversely, the quantum-mechanical shell effects help to stabilize them. There are theoretical models for predicting the masses of yet-to-be-discovered superheavy elements, based on such shell effects, and these models can be tested by studying the shells of known actinide nuclei. The problem is that current mass values determined from studying radioactive decay products have substantial errors. <jats:bold> Minaya Ramirez <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="1207" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225636">1207</jats:related-article> , published online 9 August; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6099" page="1183" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1228467">Bollen</jats:related-article> </jats:bold> ) were able to collect a sufficient number of nuclei of lawrencium and nobelium isotopes in an ion trap to determine their masses directly by mass spectroscopy. These results will be helpful in predicting the heaviest possible element. </jats:p>

<jats:title>Nighttime Sources</jats:title> <jats:p> Organic aerosols account for about half of the total mass of small (submicrometer) particles in the troposphere, and most of them are believed to form through the oxidation of volatile molecules, rather than being emitted directly from specific sources. These particles have important roles in many atmospheric processes, and therefore a better understanding of their complex composition and chemistry is desirable. <jats:bold> Rollins <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="1210" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1221520">1210</jats:related-article> ) report on measurements of particulate organic nitrates, an important class of organic aerosols that form at night. However, they also found that high concentrations of organic molecules can suppress the growth of organic nitrate particles. These observations should help improve efforts to reduce organic aerosol pollution. </jats:p>

<jats:title>Evolving Group Formation</jats:title> <jats:p> Grouping behavior in prey species has long been thought to constitute an adaptation against predation; however, it has been difficult to characterize the mechanisms by which predator selection shapes prey movement and grouping behavior. Using an approach that combines the selection imposed by a live predator, the bluegill sunfish, with manipulation of computer-generated “prey,” <jats:bold> Ioannou <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="1212" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1218919">1212</jats:related-article> , published online 16 August; see the Perspective by <jats:bold>Romey</jats:bold> ) show that “prey” that behave as a group are more likely to survive that those that move in other ways. </jats:p>

<jats:title>Understanding a Broken Heart</jats:title> <jats:p> Cardiac myosin-binding protein C (cMyBP-C) is a thick filament–associated sarcomeric protein that modulates cardiac contractility in a phosphorylation-dependent manner; mutations in the <jats:italic>MYBC3</jats:italic> gene are the leading cause of hypertrophic cardiomyopathy. <jats:bold> Previs <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="1215" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1223602">1215</jats:related-article> , published online 23 August; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6099" page="1182" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1227943">Burghardt and Ajtai</jats:related-article> </jats:bold> ) have isolated native myosin thick filaments from transgenic mouse hearts, which retained the spatial distribution of cMyBP-C in the thick filament. Imaging of a single actin filament being propelled along the thick filament showed that the N-terminal 29-kD domain of cMyBP-C slows actomyosin motion in parts of the thick filament corresponding to the C-zones in which the thick filaments are cross-bridged. This effect on actomyosin contractility was tuned by graded phosphorylation of four serines adjacent to the 29-kD domain. The findings may explain the appearance of a cMyBP-C fragment in the serum of patients with cardiac ischemia and why cMyBP-C haploinsufficiency associated with cardiomyopathy patients might trigger a hypertrophic response. </jats:p>