Catálogo de publicaciones - revistas

<jats:title>Filling a Cavity</jats:title> <jats:p> Unlike liquid ammonia, water cannot sustain a steady concentration of isolated electrons. Nonetheless, high-energy irradiation can introduce a small number of free charges that engage in potent reductive chemistry and have clear spectroscopic signatures. The manner in which water solubilizes these hydrated electrons has remained uncertain, but the general consensus has been that repulsive interactions drive the nearest water molecules away, leaving the electron in a nearly spherical empty cavity. <jats:bold> Larsen <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="65" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1189588">65</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5987" page="42" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191707">Jordan and Johnson</jats:related-article> ) upend this consensus with simulations based on a more thorough potential function for modeling the competing attractions and repulsions between the electron and surrounding water. The calculations suggest that the hydrated electron actually draws water in, occupying a region denser than the pure bulk liquid. The model reproduces experimental spectral and dynamic observations as effectively as, and in some cases better than, the cavity framework. </jats:p>

<jats:title>Early Rising Hydrogen</jats:title> <jats:p> Formation of molecular hydrogen through electron-expelling collisions of H atoms and H <jats:sup>−</jats:sup> anions is regarded as a key step in the cooling process that led to assembly of the first stars in the early universe. <jats:bold> Kreckel <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="69" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1187191">69</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article issue="5987" page="" related-article-type="in-this-issue" vol="329">Bromm</jats:related-article> </jats:bold> ) performed highly precise laboratory measurements of the rate of this reaction at a range of different energies. The study required construction of a dedicated apparatus to carefully tune the relative velocity of merged atom and ion beams. The data validated prior theoretically calculated reaction cross sections, which were then extended for use in cosmological models. </jats:p>

<jats:title>No Genetic Vertigo</jats:title> <jats:p> Peoples living in high altitudes have adapted to their situation (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5987" page="40" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192481">Storz</jats:related-article> </jats:bold> ). To identify gene regions that might have contributed to high-altitude adaptation in Tibetans, <jats:bold> Simonson <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="72" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1189406">72</jats:related-article> , published online 13 May) conducted a genome scan of nucleotide polymorphism comparing Tibetans, Han Chinese, and Japanese, while <jats:bold> Yi <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="75" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1190371">75</jats:related-article> ) performed comparable analyses on the coding regions of all genes—their exomes. Both studies converged on a gene, <jats:italic>endothelial Per-Arnt-Sim domain protein 1</jats:italic> (also known as <jats:italic>hypoxia-inducible factor 2</jats:italic> α), which has been linked to the regulation of red blood cell production. Other genes identified that were potentially under selection included adult and fetal hemoglobin and two functional candidate loci that were correlated with low hemoglobin concentration in Tibetans. Future detailed functional studies will now be required to examine the mechanistic underpinnings of physiological adaptation to high altitudes. </jats:p>

<jats:title>No Genetic Vertigo</jats:title> <jats:p> Peoples living in high altitudes have adapted to their situation (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5987" page="40" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192481">Storz</jats:related-article> </jats:bold> ). To identify gene regions that might have contributed to high-altitude adaptation in Tibetans, <jats:bold> Simonson <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="72" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1189406">72</jats:related-article> , published online 13 May) conducted a genome scan of nucleotide polymorphism comparing Tibetans, Han Chinese, and Japanese, while <jats:bold> Yi <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="75" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1190371">75</jats:related-article> ) performed comparable analyses on the coding regions of all genes—their exomes. Both studies converged on a gene, <jats:italic>endothelial Per-Arnt-Sim domain protein 1</jats:italic> (also known as <jats:italic>hypoxia-inducible factor 2</jats:italic> α), which has been linked to the regulation of red blood cell production. Other genes identified that were potentially under selection included adult and fetal hemoglobin and two functional candidate loci that were correlated with low hemoglobin concentration in Tibetans. Future detailed functional studies will now be required to examine the mechanistic underpinnings of physiological adaptation to high altitudes. </jats:p>

<jats:title>Erasing Markers</jats:title> <jats:p> Epigenetic reprogramming of the mammalian genome, which involves the removal and replacement of the various regulatory epigenetic marks such as DNA methylation, occurs during germ cell differentiation and during early zygotic development. This process is also critical during the experimental generation of stem cells, but the factors and pathways that control epigenetic reprogramming are not well understood. <jats:bold> Hajkova <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="78" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1187945">78</jats:related-article> ) investigated the erasure of DNA methylation during germ cell differentiation and during early zygotic development in the developing mouse and found that factors involved in the base excision repair (BER) pathway, which helps repair damaged DNA, were involved. Furthermore, inhibitors of BER resulted in the retention of DNA methylation in the zygote. </jats:p>

<jats:title>Dodgy Repair</jats:title> <jats:p> A double-strand break (DSB) in genomic DNA poses a serious threat to genome stability, and yet vertebrate cells may suffer 10 or more DSBs every time the genome is replicated. Pathways have thus evolved that can recognize and repair DSBs before they reek havoc in the cell. <jats:bold> Hicks <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="82" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191125">82</jats:related-article> ) show that this repair can come at a price. DSBs were induced in the budding yeast genome. Repair of a break was accompanied by a massive increase in the rate of mutation in the vicinity of the break. The mutations generated displayed a specific “signature” that included the copying of divergent sequences from other chromosomes. </jats:p>

<jats:title>One Two T</jats:title> <jats:p> T cells develop in the thymus, where they proceed through several developmental stages, losing alternative lineage potential as they progress. The molecular regulation of this developmental process, however, is not fully understood (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5987" page="44" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191664">Di Santo</jats:related-article> </jats:bold> ). <jats:bold> P. Li <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="85" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188063">85</jats:related-article> , published online 10 June), <jats:bold> L. Li <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="89" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188989">89</jats:related-article> ), and <jats:bold> Ikawa <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="93" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188995">93</jats:related-article> ) now identify expression of the zinc finger transcription factor <jats:italic>Bcl11b</jats:italic> as the earliest checkpoint in T cell development in mice. Genetic deletion of <jats:italic>Bcl11b</jats:italic> in developing T cells inhibited commitment to the T cell lineage. Under conditions that should have stimulated T lineage differentiation, <jats:italic>Bcl11b</jats:italic> -deficient T cell progenitors failed to up-regulate genes associated with lineage-committed T cells and maintained stem cell– and progenitor cell–associated gene expression. In both developing and committed T cells, loss of <jats:italic>Bcl11b</jats:italic> resulted in the generation of cells that resembled natural killer (NK) cells in both phenotype and function. These NK-like cells could be expanded easily in vitro and possessed antitumor cytotoxicity, but they did not exhibit cytotoxicity against normal cells and were not tumorigenic. Because T cells are much easier to obtain from human patients than NK cells, deletion of <jats:italic>Bcl11b</jats:italic> in T cells may thus provide a source of easy-to-grow NK cells for cell-based antitumor therapies. </jats:p>

<jats:title>One Two T</jats:title> <jats:p> T cells develop in the thymus, where they proceed through several developmental stages, losing alternative lineage potential as they progress. The molecular regulation of this developmental process, however, is not fully understood (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5987" page="44" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191664">Di Santo</jats:related-article> </jats:bold> ). <jats:bold> P. Li <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="85" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188063">85</jats:related-article> , published online 10 June), <jats:bold> L. Li <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="89" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188989">89</jats:related-article> ), and <jats:bold> Ikawa <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="93" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188995">93</jats:related-article> ) now identify expression of the zinc finger transcription factor <jats:italic>Bcl11b</jats:italic> as the earliest checkpoint in T cell development in mice. Genetic deletion of <jats:italic>Bcl11b</jats:italic> in developing T cells inhibited commitment to the T cell lineage. Under conditions that should have stimulated T lineage differentiation, <jats:italic>Bcl11b</jats:italic> -deficient T cell progenitors failed to up-regulate genes associated with lineage-committed T cells and maintained stem cell– and progenitor cell–associated gene expression. In both developing and committed T cells, loss of <jats:italic>Bcl11b</jats:italic> resulted in the generation of cells that resembled natural killer (NK) cells in both phenotype and function. These NK-like cells could be expanded easily in vitro and possessed antitumor cytotoxicity, but they did not exhibit cytotoxicity against normal cells and were not tumorigenic. Because T cells are much easier to obtain from human patients than NK cells, deletion of <jats:italic>Bcl11b</jats:italic> in T cells may thus provide a source of easy-to-grow NK cells for cell-based antitumor therapies. </jats:p>

<jats:title>One Two T</jats:title> <jats:p> T cells develop in the thymus, where they proceed through several developmental stages, losing alternative lineage potential as they progress. The molecular regulation of this developmental process, however, is not fully understood (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5987" page="44" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191664">Di Santo</jats:related-article> </jats:bold> ). <jats:bold> P. Li <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="85" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188063">85</jats:related-article> , published online 10 June), <jats:bold> L. Li <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="89" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188989">89</jats:related-article> ), and <jats:bold> Ikawa <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="93" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1188995">93</jats:related-article> ) now identify expression of the zinc finger transcription factor <jats:italic>Bcl11b</jats:italic> as the earliest checkpoint in T cell development in mice. Genetic deletion of <jats:italic>Bcl11b</jats:italic> in developing T cells inhibited commitment to the T cell lineage. Under conditions that should have stimulated T lineage differentiation, <jats:italic>Bcl11b</jats:italic> -deficient T cell progenitors failed to up-regulate genes associated with lineage-committed T cells and maintained stem cell– and progenitor cell–associated gene expression. In both developing and committed T cells, loss of <jats:italic>Bcl11b</jats:italic> resulted in the generation of cells that resembled natural killer (NK) cells in both phenotype and function. These NK-like cells could be expanded easily in vitro and possessed antitumor cytotoxicity, but they did not exhibit cytotoxicity against normal cells and were not tumorigenic. Because T cells are much easier to obtain from human patients than NK cells, deletion of <jats:italic>Bcl11b</jats:italic> in T cells may thus provide a source of easy-to-grow NK cells for cell-based antitumor therapies. </jats:p>

<jats:p>The show includes genetic signatures of long life, concerns about synthetic biology, behavioral epigenetics, and more.</jats:p>