Catálogo de publicaciones - revistas

<jats:title>Fabrication goes for a quick spin</jats:title> <jats:p> Most 3D printing techniques involve adding material layer by layer. This sets some limitations on the types of applications for which 3D printing is suitable, such as printing around a preexisting object. Kelly <jats:italic>et al.</jats:italic> present a different method for manufacturing by rotating a photopolymer in a dynamically evolving light field (see the Perspective by Hart and Rao). This allowed them to print entire complex objects through one complete revolution, circumventing the need for layering. The method may be particularly useful for high-viscosity photopolymers and multimaterial fabrication. </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="6431" page="1075" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau7114">1075</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6431" page="1042" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw7062">1042</jats:related-article> </jats:p>

<jats:title>Resetting the glacial timer</jats:title> <jats:p> The periodicity of glacial cycles changed from 100,000 to 41,000 years during the middle of the Pleistocene epoch. Why? Hasenfratz <jats:italic>et al.</jats:italic> measured the oxygen isotope composition and magnesium/calcium ratio in benthic and planktonic foraminifera from the Antarctic in order to reconstruct changes in the rate of transfer of ocean water from the depths to the surface over the past 1.5 million years (see the Perspective by Menviel). The emergence of the 100,000-year cycle coincided with a reduction in deep-water supply and a freshening of the surface ocean. This slowing may have caused more prolonged ice ages by making the Antarctic less responsive to orbitally paced drivers of carbon dioxide release. </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="6431" page="1080" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aat7067">1080</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6431" page="1040" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw7196">1040</jats:related-article> </jats:p>

<jats:title>Regulating HSC progenitors via cholesterol</jats:title> <jats:p> Atherosclerosis is characterized by the buildup of cholesterol-containing lipoproteins in the vascular wall. This increased cholesterol augments hematopoietic stem and progenitor cell (HSPC) counts, and the resultant increase in leukocytes is associated with increased cardiovascular disease. Gu <jats:italic>et al.</jats:italic> describe a mechanism orchestrating HSPC specification from the hemogenic endothelium (HE) during embryogenesis (see the Perspective by Rajan and Berman). ApoA-I binding protein accelerated cholesterol efflux from the HE, activating the transcription factor Srebp2, which in turn transactivated Notch signaling. This mechanism also appears to be important for adult HSPC expansion in hypercholesterolemia. </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="6431" page="1085" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav1749">1085</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6431" page="1041" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw7059">1041</jats:related-article> </jats:p>

<jats:title>Akt produces reducing power</jats:title> <jats:p> The protein kinase Akt provides a link from growth factors to the production of metabolic reducing power within the cell. Hoxhaj <jats:italic>et al.</jats:italic> discovered that Akt directly phosphorylates nicotinamide adenine dinucleotide kinase (NADK). Catalytic activity of NADK is normally inhibited by its own amino-terminal domain, and phosphorylation by Akt relieved this inhibition. Active NADK produces nicotinamide adenine dinucleotide phosphate (NADP <jats:sup>+</jats:sup> ). NADP <jats:sup>+</jats:sup> in turn is required to produce the reduced form of NADP <jats:sup>+</jats:sup> (NADPH), which is the primary cofactor for reductive metabolism in the cell. </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="6431" page="1088" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau3903">1088</jats:related-article> </jats:p>

<jats:title>Organized for action</jats:title> <jats:p> It is becoming increasingly clear that biomolecular condensates, which are concentrations of macromolecules not surrounded by a membrane, are a key organizational structure in eukaryotic cells (see the Perspective by Martin and Mittag). Now, two papers show how such condensates function in actin assembly or in a Ras signaling pathway. In both cases, the condensates form at the plasma membrane and increase the activity of signaling proteins by increasing their membrane dwell times. Case <jats:italic>et al.</jats:italic> show that the dwell time is dependent on cluster stoichiometry, so that stoichiometry of regulatory proteins can control actin assembly. Huang <jats:italic>et al.</jats:italic> demonstrate that the longer dwell time allows kinetic proofreading in receptor-mediated activation of Ras. </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="6431" page="1093" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau6313">1093</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6431" page="1098" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau5721">1098</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6431" page="1036" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw6434">1036</jats:related-article> </jats:p>

<jats:title>Organized for action</jats:title> <jats:p> It is becoming increasingly clear that biomolecular condensates, which are concentrations of macromolecules not surrounded by a membrane, are a key organizational structure in eukaryotic cells (see the Perspective by Martin and Mittag). Now, two papers show how such condensates function in actin assembly or in a Ras signaling pathway. In both cases, the condensates form at the plasma membrane and increase the activity of signaling proteins by increasing their membrane dwell times. Case <jats:italic>et al.</jats:italic> show that the dwell time is dependent on cluster stoichiometry, so that stoichiometry of regulatory proteins can control actin assembly. Huang <jats:italic>et al.</jats:italic> demonstrate that the longer dwell time allows kinetic proofreading in receptor-mediated activation of Ras. </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="6431" page="1093" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau6313">1093</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6431" page="1098" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau5721">1098</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6431" page="1036" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw6434">1036</jats:related-article> </jats:p>

<jats:title>Crystal structure of the KDEL receptor</jats:title> <jats:p> Eukaryotic cells concentrate chaperones in the lumen of the endoplasmic reticulum (ER). These chaperones can be swept along the secretory pathway to the Golgi apparatus, from where they must be returned. For 20 years, cell biologists have known the identity of the KDEL (Lys-Asp-Glu-Leu) receptor responsible for this process, but the molecular basis for its function has remained elusive. Now, Bräuer <jats:italic>et al.</jats:italic> present crystal structures of the KDEL receptor, in both the apo ER state and KDEL retrieval signal–bound Golgi state. Comparisons of these two states identify the conformational switch that exposes the ER retrieval motif. The authors recapitulated the binding and release cycle of the receptor using purified components, confirming that the receptor is the minimal component required to bind KDEL ligands in the Golgi. </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="6431" page="1103" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw2859">1103</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>