Catálogo de publicaciones - revistas

<jats:title>Dissecting Ephrin-Receptor Interaction</jats:title> <jats:p> Ephrins are transmembrane proteins that bind ephrin receptors on adjacent cells, leading to propagation of biochemical signals within both cells. <jats:bold> Jørgensen <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="1502" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1176615">1502</jats:related-article> ) devised a way to use differential isotopic labeling to distinguish cells engineered to express either the receptor or the ligand and to monitor bidirectional signaling events by mass spectrometry of the labeled peptides when the cells were mixed together. Signaling networks were constructed, and the information processing by the two interacting cell types was modeled. Changes in signaling within cells expressing just the ligand (ephrin) caused changes in the signal processing during the adjacent cell's response to binding of the ephrin receptor. </jats:p>

<jats:title>TAL Order</jats:title> <jats:p> <jats:italic>Xanthomonas</jats:italic> bacteria attack their plant hosts by delivering their own transcription-activator–like (TAL) proteins into the plant cell nucleus and alter the plant's gene regulation (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5959" page="1491" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1183604"> <jats:bold>Voytas and Joung</jats:bold> </jats:related-article> </jats:bold> ). <jats:bold>Moscou and Bogdanove</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1501" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178817">1501</jats:related-article> , published online 29 October: see the cover) and <jats:bold> Boch <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="1509" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178811">1509</jats:related-article> , published online 29 October) have now discovered how the similar but not identical repeats in the TAL proteins encode the specificity needed for the proteins to find their targets. Each repeat is specific for one DNA base pair, a specificity encoded by hypervariable amino acid positions. Combining several repeats with different amino acids in the hypervariable positions allowed the production of new effectors that targeted new DNA sites. </jats:p>

<jats:title>Microquasar Spotted</jats:title> <jats:p> Microquasars are binary star systems where a normal star sheds matter onto a neutron star or a black hole, generating x-ray radiation and jets of material moving at relativistic speeds. Microquasars have proved difficult to detect in high-energy gamma rays (&gt; 100 megaelectron volts). Using the Fermi Large Area Telescope, <jats:bold> Abdo <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="1512" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1182174">1512</jats:related-article> , published online 26 November; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5959" page="1490" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1184534">Bignami</jats:related-article> </jats:bold> ) now report the detection of variable gamma-ray emission from the microquasar Cygnus X-3. The gamma-ray flux is modulated at the orbital period of Cygnus X-3, and its variation is correlated with the radio emission originating from the microquasar's relativistic jets. </jats:p>

<jats:title>Flexible Organic Flash Memory</jats:title> <jats:p> Advances in organic electronics have enabled the fabrication of a number of core devices on flexible plastic substrates. These include transistors, light-emitting diodes, actuators, and sensors. <jats:bold> Sekitani <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="1516" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1179963">1516</jats:related-article> ) use a low-temperature hybrid dielectric based on a thin metal oxide and a self-assembled monolayer to develop flexible floating-gate memory transistors with small program and erase voltages. These are integrated into a flexible large-area sensor area, capable of storing values from applied external pressures. </jats:p>

<jats:title>Quick Spin Flips</jats:title> <jats:p> Quantum computation holds the tantalizing promise of vastly improving the efficiency of traditional computers. Among the many solid-state candidates for storing and manipulating quantum information, nitrogen vacancy centers in diamond are especially attractive because they can be used at room temperature and stay operational for milliseconds at a time. To use this coherence time efficiently, it is important to achieve fast manipulation of the spins in the system. <jats:bold> Fuchs <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="1520" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181193">1520</jats:related-article> , published online 19 November; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5959" page="1489" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1183659"> <jats:bold>Gerardot and Öhberg</jats:bold> </jats:related-article> </jats:bold> ) used pulses of strong microwave magnetic field to probe the dynamics of single spins in a nitrogen vacancy center. In this “strong-driving” nonlinear regime, extremely quick spin flips of less than a nanosecond in duration were observed, offering the possibility that up to a million operations could be performed on a single spin during its coherence time. </jats:p>

<jats:title>Gas Leak Inspection</jats:title> <jats:p> The solid portion of Earth was formed from accretion of material and debris formed in the primitive Solar System. Earth's early evolution included the differentiation of its interior and the development of a primordial atmosphere. Heavy noble gases in the atmosphere could have been acquired during the initial accretion process or may have accumulated later through gravitational volatile capture. <jats:bold> Holland <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="1522" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1179518">1522</jats:related-article> ) show that Kr and Xe trapped in the upper mantle have isotopic signatures characteristic of early Solar System material similar to meteorites rather than those of the modern atmosphere and oceans. Thus, noble gases trapped within the young Earth did not contribute to Earth's later atmospheric composition. </jats:p>

<jats:title>Framework for Change</jats:title> <jats:p> Organic aerosols make up 20 to 90% of the particulate mass of the troposphere and are important factors in both climate and human heath. However, their sources and removal pathways are very uncertain, and their atmospheric evolution is poorly characterized. <jats:bold> Jimenez <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="1525" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1180353">1525</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="5959" page="1493" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1183158">Andreae</jats:related-article> </jats:bold> ) present an integrated framework of organic aerosol compositional evolution in the atmosphere, based on model results and field and laboratory data that simulate the dynamic aging behavior of organic aerosols. Particles become more oxidized, more hygroscopic, and less volatile with age, as they become oxygenated organic aerosols. These results should lead to better predictions of climate and air quality. </jats:p>

<jats:title>Early Dinosaur Discovery</jats:title> <jats:p> Our understanding of the evolution of early dinosaurs is hampered by limited material, especially compared to the many Jurassic and Cretaceous samples. <jats:bold> Nesbitt <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="1530" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1180350">1530</jats:related-article> ) provide a complete view of a Late Triassic theropod based on several nearly complete skeletons from New Mexico. The dinosaur elucidates the likely relationships between early theropods and shows that some prominent features were already derived by this time. Comparison among Triassic dinosaur fauna and other early species suggests that Triassic North American fauna were diverse but not endemic, perhaps arising from earlier migrants from South America. </jats:p>

<jats:title>Dissecting Amyloid Formation</jats:title> <jats:p> Amyloid fibrils are associated with clinical disorders ranging from Alzheimer's disease to type II diabetes. Their self-assembly can be described by a master equation that takes into account nucleation-dependent polymerization and fragmentation. <jats:bold> Knowles <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="1533" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1178250">1533</jats:related-article> ) now present an analytical solution to the master equation, which shows that amyloid growth kinetics is often limited by the fragmentation rate rather than by the rate of primary nucleation. In addition, the results reveal relationships between system properties (scaling laws) that provide mechanistic insight not only into amyloid growth, but also into related self-assembly processes. </jats:p>

<jats:title>Understanding Hybrid Sterility</jats:title> <jats:p> The onset of reproductive barriers, or hybrid sterility, is a means of reinforcing genetic incompatibilities between isolated populations, leading to speciation. A handful of genes that underlie hybrid sterility have been discovered, but their molecular mechanism is generally unclear. <jats:bold>Bayes and Malik</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1538" related-article-type="in-this-issue" vol="326" xlink:href="10.1126/science.1181756">1538</jats:related-article> , published online 22 October) reveal that the hybrid sterility gene <jats:italic>Odysseus-site Homeobox (OdsH)</jats:italic> , which encodes a satellite-DNA binding protein, shows differential DNA binding patterns between the species <jats:italic>Drosophila mauritiana</jats:italic> and <jats:italic>D. simulans</jats:italic> ; OdsH derived from <jats:italic>D. mauritiana</jats:italic> localizes to the <jats:italic>D. simulans</jats:italic> Y chromosome, whereas OdsH derived from <jats:italic>D. simulans</jats:italic> does not. The incorrect expression, localization, and endurance of the OdsH protein appear to affect spermatogenesis in hybrid males, explaining the mechanism underlying hybrid sterility between these species. Thus, genetic incompatibilities between satellite-DNA and their binding proteins may represent a general basis for hybrid sterility in animals. </jats:p>