Catálogo de publicaciones - revistas

<jats:title>Complex regulation</jats:title> <jats:p> The protein kinase mTORC1 controls cellular growth in response to external signals. In the presence of nutrients, it localizes on the surface of the lysosome, where it is activated. The Raptor domain of mTORC1 binds to a complex comprising the protein Ragulator and a heterodimer of the Rag guanosine triphosphatase, which can adopt four different nucleotide conformations depending on nutrient availability. Rogala <jats:italic>et al.</jats:italic> determined the structure of the Raptor-Rag-Ragulator complex at 3.2-angstrom resolution by cryo–electron microscopy. The structure shows why Raptor binds only to a specific nucleotide conformation of the Rag heterodimer and suggests a model for how mTORC1 would dock onto the lysosomal surface, which is a key step in its activation. </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="6464" page="468" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay0166">468</jats:related-article> </jats:p>

<jats:title>Flexible ferroelectrics</jats:title> <jats:p> High-quality ferroelectric materials, which polarize in response to an electric field, are usually oxides that crack when bent. Dong <jats:italic>et al.</jats:italic> found that high-quality membranes of barium titanate are surprisingly flexible and super-elastic. These films accommodate large strains through dynamic evolution of nanodomains during deformation. This discovery is important for developing more robust flexible devices. </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="6464" page="475" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay7221">475</jats:related-article> </jats:p>

<jats:title>Earthworm distribution in global soils</jats:title> <jats:p> Earthworms are key components of soil ecological communities, performing vital functions in decomposition and nutrient cycling through ecosystems. Using data from more than 7000 sites, Phillips <jats:italic>et al.</jats:italic> developed global maps of the distribution of earthworm diversity, abundance, and biomass (see the Perspective by Fierer). The patterns differ from those typically found in aboveground taxa; there are peaks of diversity and abundance in the mid-latitude regions and peaks of biomass in the tropics. Climate variables strongly influence these patterns, and changes are likely to have cascading effects on other soil organisms and wider ecosystem functions. </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="6464" page="480" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aax4851">480</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6464" page="425" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz5670">425</jats:related-article> </jats:p>

<jats:title>Milling corundum nanoparticles</jats:title> <jats:p> High-purity corundum (α-Al <jats:sub>2</jats:sub> O <jats:sub>3</jats:sub> ) nanoparticles could enable applications such as more stable catalyst supports or precursors for high-strength ceramics. Milling of corundum only produces micrometer-scale particles, and direct synthesis from other aluminum oxides that would be likely starting materials, such as γ-Al <jats:sub>2</jats:sub> O <jats:sub>3</jats:sub> , fails because of the high activation barrier for converting the lattice structure of these cubic close-packed oxides. Amrute <jats:italic>et al.</jats:italic> show that ball milling of boehmite, γ-AlOOH, created ∼13-nanometer-diameter corundum nanoparticles of high purity through a mechanically induced dehydration reaction and by the effect of milling impacts on the surface energy of the particles. </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="6464" page="485" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaw9377">485</jats:related-article> </jats:p>

<jats:title>Genetic background affects variation</jats:title> <jats:p> Robustness, or the effect of mutations on fitness, can affect the evolutionary trajectory of a species. By introducing a large number of deleterious mutations into many different genetic backgrounds of yeast, Johnson <jats:italic>et al.</jats:italic> found that, for many mutations, the more fit the background, the larger the deleterious effect of the mutation (see the Perspective by Miller). A more-fit lineage is thus less tolerant to deleterious mutations, whereas less-fit lineages can tolerate more mutations. This observation supports a tendency toward diminishing returns for beneficial mutations, which has been shown to influence patterns of adaptation. </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="6464" page="490" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay4199">490</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6464" page="418" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz5189">418</jats:related-article> </jats:p>

<jats:title>Commensals rule the MAITrix</jats:title> <jats:p> Mucosal-associated invariant T (MAIT) cells play an important role in mucosal homeostasis. MAIT cells recognize microbial small molecules presented by the major histocompatibility complex class Ib molecule MR1. MAIT cells are absent in germ-free mice, and the mechanisms by which microbiota control MAIT cell development are unknown (see the Perspective by Oh and Unutmaz). Legoux <jats:italic>et al.</jats:italic> show that, in mice, development of MAIT cells within the thymus is governed by the bacterial product 5-(2-oxopropylideneamino)-6- <jats:sc>d</jats:sc> -ribitylaminouracil, which rapidly traffics from the mucosa to the thymus, where it is captured by MR1 and presented to developing MAIT cells. Constantinides <jats:italic>et al.</jats:italic> report that MAIT cell induction only occurs during a limited, early-life window and requires exposure to defined microbes that produce riboflavin derivatives. Continual interactions between MAIT cells and commensals in the skin modulates tissue repair functions. Together, these papers highlight how the microbiota can direct immune cell development and subsequent function at mucosal sites by secreting compounds that act like self-antigens. </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="6464" page="494" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaw2719">494</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" related-article-type="in-this-issue" xlink:href="10.1126/science.aax6624">eaax6624</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6464" page="419" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aaz4014">419</jats:related-article> </jats:p>

<jats:title>Alternative influenza target</jats:title> <jats:p> There is a pressing need for a broadly protective influenza vaccine that can neutralize this constantly varying, deadly virus. Stadlbauer <jats:italic>et al.</jats:italic> turned their attention away from the current vaccine target—the mutable hemagglutinin—and investigated an alternative, less variable virus-coat glycoprotein: neuraminidase. The authors extracted monoclonal antibodies (mAbs) from a human donor naturally infected with the H3N2 virus subtype. In mice, the mAbs were broadly protective against influenza virus A groups 1 and 2 (human, avian, and swine origin) and some influenza B viruses. These mAbs were also therapeutically effective as late as 72 hours after infection. The wide range of reactivity probably relates to the infection history of the donor, whose plasmablasts generated antibodies with long regions that insert into the active site of the neuraminidase enzyme. </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="6464" page="499" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay0678">499</jats:related-article> </jats:p>

<jats:title>Coupled transport</jats:title> <jats:p> Cation-chloride cotransporters move chloride and cations across the cell membrane and are important in regulating cell volume and setting the chloride concentration inside the cell. Mutations lead to serious diseases, such as epilepsy. Liu <jats:italic>et al.</jats:italic> present the structure of the human potassium-chloride cotransporter KCC1, as determined by cryo–electron microscopy. Based on the structure, functional studies, and molecular dynamics simulations, they propose an ion transport model. The structure provides a framework for interpreting disease-related mutations in potassium-chloride cotransporters. </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="6464" page="505" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay3129">505</jats:related-article> </jats:p>

<jats:title>Coherent surface spin manipulation</jats:title> <jats:p> Spin-based quantum information processing requires coherent spin manipulation. Yang <jats:italic>et al.</jats:italic> demonstrate coherent control of surface titanium and iron atom spins on a magnesium oxide surface with a magnetic scanning tunneling microscope tip. Arbitrary sequences of fast electrical pulses delivered to the top induced large electric fields. These fields drove metal-atom movement, which then modulated the tip-atom exchange interaction to create an oscillating effective magnetic field. Advanced spin-control protocols such as Ramsey fringes and Hahn spin echoes revealed quantum dynamics, such as coherent oscillations in a titanium atom dimer assembled on the surface with the tip. </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="6464" page="509" related-article-type="in-this-issue" vol="366" xlink:href="10.1126/science.aay6779">509</jats:related-article> </jats:p>

<jats:p> This issue of <jats:italic>Science</jats:italic> includes the program of the 2020 AAAS Annual Meeting. The theme of the AAAS Annual Meeting in Seattle, WA, 13 to 16 February 2020, is <jats:italic>Envisioning Tomorrow’s Earth</jats:italic> . </jats:p> <jats:p> A <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://www.sciencemag.org/cgi/reprint/362/6413/471.pdf">PDF</jats:ext-link> of the program as it appears in this issue is available here; for more information on the meeting (including registration forms and information on accommodations), please visit <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="www.aaas.org/meetings/">www.aaas.org/meetings/</jats:ext-link> . </jats:p>