Catálogo de publicaciones - revistas

<jats:title>Sleep induction through ion changes</jats:title> <jats:p> How do we switch from sleep to arousal and back? Ding <jats:italic>et al.</jats:italic> found that a combination of modulatory neurotransmitters influenced the levels of extracellular ions in the brain (see the Perspective by Landolt and Holst). This influence was not driven by changes in local neuronal firing, suggesting direct effects of the neuromodulators on extracellular ion composition. However, these changes in interstitial ion levels could switch a brain from wakefulness to sleep. Changes in extracellular ions may thus be a cause, rather than a consequence, of sleep/wake-dependent changes in neuronal 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="6285" page="550" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad4821">550</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6285" page="517" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf8178">517</jats:related-article> </jats:p>

<jats:title>Progesterone signaling in sperm</jats:title> <jats:p> Cumulus cells surrounding the ovulated egg release the female hormone progesterone, which is necessary for sperm activation in mammals. Miller <jats:italic>et al.</jats:italic> identified the human sperm progesterone receptor as the orphan enzyme ABHD2. When bound by progesterone, the ABHD2 receptor acts as a lipid hydrolase to deplete an endocannabinoid inhibitor of the plasma membrane's calcium channel. This allows the entry of calcium ions through the calcium channel to activate sperm that are then primed for fertilization. </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="6285" page="555" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad6887">555</jats:related-article> </jats:p>

<jats:title>“Normal” for the gut microbiota</jats:title> <jats:p> For the benefit of future clinical studies, it is critical to establish what constitutes a “normal” gut microbiome, if it exists at all. Through fecal samples and questionnaires, Falony <jats:italic>et al.</jats:italic> and Zhernakova <jats:italic>et al.</jats:italic> targeted general populations in Belgium and the Netherlands, respectively. Gut microbiota composition correlated with a range of factors including diet, use of medication, red blood cell counts, fecal chromogranin A, and stool consistency. The data give some hints for possible biomarkers of normal gut communities. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6285" page="560" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad3503">560</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6285" page="565" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad3369">565</jats:related-article> </jats:p>

<jats:title>“Normal” for the gut microbiota</jats:title> <jats:p> For the benefit of future clinical studies, it is critical to establish what constitutes a “normal” gut microbiome, if it exists at all. Through fecal samples and questionnaires, Falony <jats:italic>et al.</jats:italic> and Zhernakova <jats:italic>et al.</jats:italic> targeted general populations in Belgium and the Netherlands, respectively. Gut microbiota composition correlated with a range of factors including diet, use of medication, red blood cell counts, fecal chromogranin A, and stool consistency. The data give some hints for possible biomarkers of normal gut communities. </jats:p> <jats:p> <jats:italic>Science</jats:italic> , this issue pp. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6285" page="560" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad3503">560</jats:related-article> and <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6285" page="565" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad3369">565</jats:related-article> </jats:p>

<jats:title>EZ catalyst control in olefin metathesis</jats:title> <jats:p> A decade has passed since the partner-swapping chemical dance known as olefin metathesis garnered a Nobel Prize, and distinct routines continue to emerge. In general, olefins are most stable in an E configuration, with the two largest substituents diametrically opposed. However, chlorine and fluorine substituents often invert this trend, favoring the alternate Z geometry. Nguyen <jats:italic>et al.</jats:italic> report a molybdenum metathesis catalyst with ligands carefully optimized to produce Cl- and F-substituted E olefins more quickly than the more stable Z isomers. </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="6285" page="569" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf4622">569</jats:related-article> </jats:p>

<jats:title>Synthetic twists among lipids</jats:title> <jats:p> Proteins embedded in cell membranes perform a wide variety of signaling and transport functions through conformational shifts. De Poli <jats:italic>et al.</jats:italic> examined how a much smaller, simpler construct might begin to achieve similar aims (see the Perspective by Thiele and Ulrich). Specifically, they designed an artificial peptide with a photosensitive group at one end and embedded it in a phospholipid bilayer akin to a membrane. Nuclear magnetic resonance spectroscopy revealed how light-induced isomerization influenced conformational dynamics at the other end. The results point the way toward development of small-molecule–based switches in membrane environments. </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="6285" page="575" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad8352">575</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6285" page="520" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf6191">520</jats:related-article> </jats:p>

<jats:title>Iron isotopes constrain core chemistry</jats:title> <jats:p> The overall composition of Earth's core is an important constraint on the chemistry and evolution of our planet's interior. A longstanding problem has been determining the minor element contribution to its predominately iron-nickel alloy. Based on the iron isotope fractionation of various iron alloys with pressure, Shahar <jats:italic>et al.</jats:italic> find that carbon and hydrogen are probably not primary components of the core. The fractionation occurs at the high pressures of core formation, suggesting that the stable iron isotope ratios of Earth are a new and independent constraint on core composition. </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="6285" page="580" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad9945">580</jats:related-article> </jats:p>

<jats:title>Peering into a membrance oxidase</jats:title> <jats:p> Microorganisms have evolved a number of enzymes to reduce oxygen and prevent oxidative stress. Cytochrome bd oxidases serve this role and also protect pathogenic bacteria from nitric acid; however, this class of enzymes so far has eluded high-resolution crystallography. Safarian <jats:italic>et al.</jats:italic> were able to resolve the three-dimensional structure of cytochrome bd oxidase from a thermophilic bacterium (see the Perspective by Cook and Poole). The overall structure and triangular arrangement of its heme cofactors bear little structural resemblance to those of other membrane-spanning oxidases, despite serving a similar function. </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="6285" page="583" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf2477">583</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6285" page="518" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf5514">518</jats:related-article> </jats:p>

<jats:title>Persistence of fecal transplants</jats:title> <jats:p> Fecal microbiota transplantation is a successful way of treating the distressing symptoms of irritable bowel disease or <jats:italic>Clostridium difficile</jats:italic> infection. The procedure is done by administering a concentrate of colonic bacteria from a healthy donor. Li <jats:italic>et al.</jats:italic> used metagenomic data to look at single-nucleotide variants after transplants in humans. Donor and recipient strains coexisted for at least 3 months. Some donor strains replaced related strains of the same species, but totally novel species from a donor were unlikely to thrive in a recipient. Rational design of personalized fecal transplant “cocktails” will therefore rely on resolution beyond the species level. </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="6285" page="586" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad8852">586</jats:related-article> </jats:p>