Catálogo de publicaciones - revistas

<jats:title>Breaking the symmetry in an atomic gas</jats:title> <jats:p> Cooling a physical system through a phase transition typically makes it less symmetrical. If the cooling is done very slowly, this symmetry change is uniform throughout the system. For a faster cooling process, the system breaks up into domains: The faster the cooling, the smaller the domains. Navon <jats:italic>et al.</jats:italic> studied this process in an ultracold gas of Rb atoms near its transition to a condensed state (see the Perspective by Ferrari). The authors found that the size of the domains froze in time in the vicinity of the transition and that it depended on the cooling speed, as predicted by theory. </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="6218" page="167" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1258676">167</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6218" page="127" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa3016">127</jats:related-article> </jats:p>

<jats:title>Gut microbes resist inflammation</jats:title> <jats:p> It is vital to human well-being that our gut microbiota can be distinguished from harmful, but often very similar, organisms. Cullen <jats:italic>et al.</jats:italic> begin to analyze how one dominant symbiont, <jats:italic>Bacteroidetes thetaiotaomicron</jats:italic> , does this. Our guts release potent antimicrobial peptides when we become infected with pathogenic bacteria such as salmonella, but these symbionts make an outer lipopolysaccharide coat that differs from those of pathogens by only one phosphate molecule. Enzymatic removal of this group is enough to confer resistance to the host's immune response and allow the symbionts to escape damage. </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="6218" page="170" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260580">170</jats:related-article> </jats:p>

<jats:title>Co-infection complicates treatment</jats:title> <jats:p>Infections rarely occur in isolation, and treating one pathogen may have unpredictable effects on another. Ezenwa and Jolles, working on wild African buffaloes, expected that because deworming relieves immune suppression, such treatment would lead to a drop in tuberculosis because the animals would clear the second infection without further intervention. Not so. Deworming did improve the lot of parasite-infested individuals, but it also increased the spread of tuberculosis among the population. What apparently happened is that the worm-free buffalo lived longer but stayed infected with tuberculosis and had longer to spread the infection among the herd.</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="6218" page="175" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261714">175</jats:related-article> </jats:p>

<jats:title>Dueling dimers serve dual purposes</jats:title> <jats:p> Both bacteria and mitochrondria produce NADPH for amino acid biosynthesis and to remove reactive oxygen species. The enzyme that makes NADPH must translocate a proton across the membrane and transfer a hydride from NADH to NADP <jats:sup>+</jats:sup> —processes that happen some 40 Å apart. To understand this complex geometry, Leung <jats:italic>et al.</jats:italic> solved the structures of the entire transhydrogenase enzyme and the membrane domain from the bacterium <jats:italic>Thermus thermophilus</jats:italic> (see the Perspective by Krengel and Törnroth-Horsefield). The entire enzyme exists as a dimer, with the two membrane domains in alternate orientations. One of the membrane domains interacts with the membrane component for proton translocation, whereas the other domain exchanges hydride with NAD(H) in another large soluble domain. </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="6218" page="178" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1260451">178</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6218" page="125" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa3602">125</jats:related-article> </jats:p>

<jats:title>Dating the influence of Deccan Traps eruptions</jats:title> <jats:p> The Deccan Traps flood basalts in India represent over a million cubic kilometers of erupted lava. These massive eruptions occurred around the same time as the end-Cretaceous mass extinction some 65 million years ago, which famously wiped out all nonavian dinosaurs. Schoene <jats:italic>et al.</jats:italic> determined the precise timing and duration of the main phase of the eruptions, which lasted over 750,000 years and occurred just 250,000 years before the Cretaceous-Paleogene boundary. The relative contribution of these eruptions and of the Chicxulub impact in Mexico to the mass extinction remains unclear, but both provide potential kill mechanisms. </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="6218" page="182" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa0118">182</jats:related-article> </jats:p>

<jats:title>A factor for repairing broken DNA</jats:title> <jats:p> Unprogrammed DNA double-strand breaks are extremely dangerous for genomic stability. Nonhomologous end-joining (NHEJ) repair systems are present in all domains of life and help deal with these potentially lethal lesions. Ochi <jats:italic>et al.</jats:italic> have discovered a new factor involved in NHEJ by searching for proteins with structural similarities to known NHEJ proteins. Specifically, PAXX, a paralog of XRCC1 and XLF, interacts with a key repair pathway protein, Ku, and helps promote ligation of the broken DNA. </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="6218" page="185" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1261971">185</jats:related-article> </jats:p>

<jats:title>Sensing amino acids at the lysosome</jats:title> <jats:p> The mTORC1 protein kinase is a complex of proteins that functions to regulate growth and metabolism. Activity of mTORC1 is sensitive to the abundance of amino acids, but how the sensing of amino acids is coupled to the control of mTORC1 has been unclear. Wang <jats:italic>et al.</jats:italic> searched for predicted membrane proteins that interacted with regulators of mTORC1. They identified a protein currently known only as SLC38A9. Interaction of SLC38A9 with mTORC1 regulators was sensitive to the presence of amino acids. SLC38A9 has sequence similarity to amino acid transporters. Effects of modulation of SLC38A9 in cultured human cells indicate that it may be the sensor that connects the abundance of arginine and leucine to mTORC1 activity. </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="6218" page="188" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1257132">188</jats:related-article> </jats:p>

<jats:title>Getting specific about amino acid sensing</jats:title> <jats:p> The protein kinase complex mTORC1 regulates growth and metabolism, and its activity is controlled in response to the abundance of cellular amino acids. Jewell <jats:italic>et al.</jats:italic> report that control of mTORC1 in response to glutamine does not require the Rag guanosine triphosphatase (GTPase) implicated in the sensing of other amino acids such as leucine (see the Perspective by Abraham). For sensing of glutamine, another GTPase, Arf1, was required. Distinct mechanisms thus appear to couple various amino acids to signaling by the mTORC1 complex. </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="6218" page="194" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.1259472">194</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6218" page="128" related-article-type="in-this-issue" vol="347" xlink:href="10.1126/science.aaa4570">128</jats:related-article> </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>

<jats:p>On this week's show: Fighting worms to battle microbes and a roundup of daily news stories.</jats:p>