Catálogo de publicaciones - revistas

<jats:title>Removing orphan proteins from the system</jats:title> <jats:p> The degradation of excess subunits of protein complexes is a major quality-control problem for the cell. How such “orphans” are recognized and tagged for degradation is poorly understood. Two papers identify a protein quality-control pathway that acts on some of the most abundant protein complexes in the human body: hemoglobin and ribosomes (see the Perspective by Hampton and Dargemont). Yanagitani <jats:italic>et al.</jats:italic> show that the central player in this process is an unusual enzyme (UBE2O) that recognizes substrates and tags them for destruction. Other quality-contr ol pathways tend to use separate factors for target selection (often a chaperone), ubiquitin donation (an E2), and ubiquitin conjugati on (an E3). Encoding all three activities in a single factor whose function can be reconstituted in a purified system provides a tractable route to detailed mechanistic and structural dissection. Nguyen <jats:italic>et al.</jats:italic> show the importance of the UBE2O pathway in the differentiation of red blood cells. </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="6350" page="472" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aan0178">472</jats:related-article> , p. <jats:related-article issue="6350" page="471" related-article-type="in-this-issue" vol="357">471</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6350" page="450" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aao1896">450</jats:related-article> </jats:p>

<jats:title>Forcing polymers to be semiconductors</jats:title> <jats:p> In mechanochemistry, the application of force to a polymer is used to pry open specific chemical bonds. Chen <jats:italic>et al.</jats:italic> leveraged this technique to produce semiconducting blocks of polyacetylene in an insulating precursor. Ring-opening metathesis polymerization tethered together a series of fused four-carbon rings, reminiscent of the unusual ladderane membrane lipids of anaerobic ammonium-oxidizing bacteria. Subsequently, sonication unzipped these strained rings into alternating C=C double bonds, thereby extending π-conjugation along the polymer backbone. </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="6350" page="475" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aan2797">475</jats:related-article> </jats:p>

<jats:title>Replacing platinum in air-fed fuel cells</jats:title> <jats:p> Replacing expensive and scarce platinum catalysts in polymer electrolyte membrane fuel cells for the oxygen reduction reaction (ORR) with ones based on non-noble metals would speed up the adoption of hydrogen fuel vehicles. Most of the candidate replacement catalysts that have shown high performance do so only when running on pure oxygen. Chung <jats:italic>et al.</jats:italic> developed an iron-nitrogen-carbon catalyst from two nitrogen precursors that forms a high-porosity structure and exhibits high ORR performance when running on air. The proposed catalytically active site is FeN <jats:sub>4</jats:sub> . </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="6350" page="479" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aan2255">479</jats:related-article> </jats:p>

<jats:title>Spin-charge separation in atomic chains</jats:title> <jats:p> Strongly interacting electrons lined up along a string can experience the so-called spin-charge separation, where the electrons “split” into effective carriers of spin and charge, which then move independently. This phenomenon has been observed, somewhat indirectly, in solids. Hilker <jats:italic>et al.</jats:italic> show spin-charge separation in a direct way by using a one-dimensional (1D) array of cold atoms, playing the role of electrons, whose degrees of freedom of spin and charge can be monitored using a fermionic quantum gas microscope. Empty sites in the 1D lattice moved freely without disturbing the underlying antiferromagnetic order. </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="6350" page="484" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aam8990">484</jats:related-article> </jats:p>

<jats:title>Linking fluids as they twist and writhe</jats:title> <jats:p> Helicity is a measure of cork-screw-like motion described by the amount of twisting, writhing, and linking in a fluid. Total helicity is conserved for ideal fluids, but how helicity changes in real fluids with even tiny amounts of viscosity has been an open question. Scheeler <jats:italic>et al.</jats:italic> provide a complete measurement of total helicity in a real fluid by using a set of hydrofoils to track linking, twisting, and writhing (see the Perspective by Moffatt). They show that twisting dissipates total helicity, whereas writhing and linking conserve it. This provides a fundamental insight into tornadogenesis, atmospheric flows, and the formation of turbulence. </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="6350" page="487" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aam6897">487</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6350" page="448" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aao1428">448</jats:related-article> </jats:p>

<jats:title>Accumulating evidence for the Zundel motif</jats:title><jats:p>In recent years, vibrational spectroscopy has been homing in on how water accommodates dissolved protons in acidic solution. Most such studies have examined adjacent stretching or bending modes. Dahms<jats:italic>et al.</jats:italic>pinpoint the vibrational dynamics of the acidic proton itself, which is sandwiched between two water molecules in a so-called Zundel motif. Comparing spectra in bulk water and in acetonitrile (a known Zundel host) revealed the persistence of this motif in aqueous acid on a subpicosecond time scale. Persistence is sustained by the hydrogen-bonding network among the surrounding water molecules.</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="6350" page="491" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aan5144">491</jats:related-article></jats:p>

<jats:title>Extreme events bring rapid change</jats:title> <jats:p> Environmental adaptation is often considered a slow process. However, extreme events, such as heat waves or cold snaps, can produce rapid changes, both morphologically and genetically. Campbell-Staton <jats:italic>et al.</jats:italic> studied a population of green anole lizards during an extreme cold snap in the southern United States (see the Perspective by Grant). After the cold snap, the lizards showed greater cold resistance and displayed changes in six genomic regions that are important for regulation of function in the cold. Understanding how extreme climatic events influence adaptive potential will become increasingly important as the climate becomes more volatile. </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="6350" page="495" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aam5512">495</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6350" page="451" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aao2067">451</jats:related-article> </jats:p>

<jats:title>Eat more plants for influenza resilience</jats:title> <jats:p> Antibiotic treatment worsens influenza in mice, possibly because the concomitant loss of the microbiota interrupts the production of bioactive metabolites. Steed <jats:italic>et al.</jats:italic> found that a microbial product, desaminotyrosine (DAT), produced by an obligate clostridial anaerobe from the digestion of plant flavonoids, is beneficial during influenza. DAT enters the bloodstream and triggers type I interferon signaling, which then augments antiviral responses by phagocytic cells. Without DAT, influenza virus causes inflammation and severe disease. </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="6350" page="498" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aam5336">498</jats:related-article> </jats:p>

<jats:title>DREADD not the designer compound</jats:title> <jats:p> Designer receptors exclusively activated by designer drugs (DREADDs) constitute a powerful chemogenetic strategy that can modulate nerve cell activity in freely moving animal preparations. Gomez <jats:italic>et al.</jats:italic> used radioligand receptor occupancy measurements and in vivo positron emission tomography to show that DREADDs expressed in the brain are not activated by the designer compound CNO (clozapine <jats:italic>N</jats:italic> -oxide). Instead, they are activated by the CNO metabolite clozapine, a drug with multiple endogenous targets. This may have important implications for the interpretation of results obtained with this popular technology. </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="6350" page="503" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aan2475">503</jats:related-article> </jats:p>

<jats:title>Hitting a dozen enzymes with one drug</jats:title> <jats:p> The adenosine monophosphate-activated protein kinase (AMPK) controls cellular energy status. AMPK is activated when energy levels fall. This stimulates adenosine triphosphate (ATP)-generating pathways that promote glucose uptake and inhibits ATP-consuming pathways associated with glucose synthesis. In principle, these effects would be beneficial in metabolic diseases, including diabetes. Pharmacological activation of AMPK has been challenging, however, because in mammals, the enzyme exists as 12 distinct complexes. Myers <jats:italic>et al.</jats:italic> describe an orally available compound (MK-8722) that activates all 12 complexes (see the Perspective by Hardie). In animal models, MK-8722 ameliorated diabetes, but it also caused enlargement of the heart. MK-8722 may be a useful tool compound for laboratory research on AMPK 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="6350" page="507" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aah5582">507</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6350" page="455" related-article-type="in-this-issue" vol="357" xlink:href="10.1126/science.aao1913">455</jats:related-article> </jats:p>