Catálogo de publicaciones - revistas

<jats:title>When two is better than four</jats:title> <jats:p> Batteries based on the reaction of zinc and oxygen have been used for more than a century, but these have been primary (that is, nonrechargeable) cells. These batteries use an alkaline electrolyte and require a four-electron reduction of oxygen to water, which is a slow process. Sun <jats:italic>et al.</jats:italic> show that with the right choice of nonalkaline electrolyte, the battery can operate using a two-electron zinc-oxygen/zinc peroxide chemistry that is far more reversible. By making the electrolyte hydrophobic, water is excluded from the near surface of the cathode, thus preventing the four-electron reduction. These batteries also show higher energy density and better cycling stability. </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="6524" page="46" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abb9554">46</jats:related-article> </jats:p>

<jats:title>Protecting the lung from hypoxic stress</jats:title> <jats:p> The lung experiences constantly changing oxygen concentrations and must recognize and respond to a low-oxygen environment. Shivaraju <jats:italic>et al.</jats:italic> reveal that airway stem cells directly sense hypoxia and respond by differentiating into protective neuroendocrine (NE) cells that secrete a peptide that mitigates tissue damage (see the Perspective by Zacharias). This work suggests that the observed NE cell hyperplasia that accompanies lung diseases such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease represents a compensatory physiologic response. More broadly, it raises the possibility that stem cells throughout the body sense hypoxia and differentiate into organ-specific NE 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="6524" page="52" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.aba0629">52</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6524" page="32" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abf4473">32</jats:related-article> </jats:p>

<jats:p>Accurate assembly of newly synthesized proteins into functional oligomers is crucial for cell activity. In this study, we investigated whether direct interaction of two nascent proteins, emerging from nearby ribosomes (co-co assembly), constitutes a general mechanism for oligomer formation. We used proteome-wide screening to detect nascent chain–connected ribosome pairs and identified hundreds of homomer subunits that co-co assemble in human cells. Interactions are mediated by five major domain classes, among which N-terminal coiled coils are the most prevalent. We were able to reconstitute co-co assembly of nuclear lamin in <jats:italic>Escherichia coli</jats:italic>, demonstrating that dimer formation is independent of dedicated assembly machineries. Co-co assembly may thus represent an efficient way to limit protein aggregation risks posed by diffusion-driven assembly routes and ensure isoform-specific homomer formation.</jats:p>

<jats:title>Checking fidelity in cell division</jats:title> <jats:p> Everything has to go right during cell division, so a checkpoint mechanism known as the spindle-assembly checkpoint prevents mitosis from proceeding unless the kinetochores that attach chromosomes to the spindle microtubules are properly engaged. Two papers now reveal the detailed molecular choreography that allows a single, unattached kinetochore to arrest cell division: Lara-Gonzalez <jats:italic>et al.</jats:italic> used a visual probe that tracks a specific form of one of the checkpoint complex proteins, and Piano <jats:italic>et al.</jats:italic> used a biochemical reconstitution of the checkpoint. Together, these studies reveal how protein interaction, spatial constraints, phosphorylation, and catalytic conversion of the protein Mad2 to its active form allow this all-important sensor to 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="6524" page="64" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abc1424">64</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6524" page="67" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abc1152">67</jats:related-article> </jats:p>

<jats:title>Checking fidelity in cell division</jats:title> <jats:p> Everything has to go right during cell division, so a checkpoint mechanism known as the spindle-assembly checkpoint prevents mitosis from proceeding unless the kinetochores that attach chromosomes to the spindle microtubules are properly engaged. Two papers now reveal the detailed molecular choreography that allows a single, unattached kinetochore to arrest cell division: Lara-Gonzalez <jats:italic>et al.</jats:italic> used a visual probe that tracks a specific form of one of the checkpoint complex proteins, and Piano <jats:italic>et al.</jats:italic> used a biochemical reconstitution of the checkpoint. Together, these studies reveal how protein interaction, spatial constraints, phosphorylation, and catalytic conversion of the protein Mad2 to its active form allow this all-important sensor to 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="6524" page="64" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abc1424">64</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6524" page="67" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abc1152">67</jats:related-article> </jats:p>

<jats:title>Finding the path to better desalination</jats:title> <jats:p> Polyamide membranes have been used in large-scale desalination for decades. However, because of the thinness of the membranes and their internal variability, it has been hard to determine which aspects of the membranes most affect their performance. Culp <jats:italic>et al.</jats:italic> combined electron tomography, nanoscale three-dimensional (3D) polyamide density mapping, and modeling of bulk water permeability with zero adjustable parameters to quantify the effect of 3D nanoscale variations in polymer mass on water transport within the polyamide membrane (see the Perspective by Geise). They found that variability in local density most affects the performance of the membranes. Better synthesis methods could thus improve performance without affecting selectivity. </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="6524" page="72" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abb8518">72</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6524" page="31" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abe9741">31</jats:related-article> </jats:p>

<jats:title>Stretching diamond to the limit</jats:title> <jats:p> Diamond is thought of as being unbendable, but thin samples can actually deform elastically. Applying relatively large amounts of strain to diamond may shift its electronic properties, which is of interest for a number of applications. Dang <jats:italic>et al.</jats:italic> elastically stretched micrometer-sized plates of diamond along different crystallographic directions. These relatively large samples show that deep-strain engineering can be accomplished in more uniform diamond specimens and may have a large impact on the electronic properties. </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="6524" page="76" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abc4174">76</jats:related-article> </jats:p>

<jats:title>Pandemic progress in Kenya</jats:title> <jats:p> By the end of July 2020, Kenya had reported only 341 deaths and ∼20,000 cases of COVID-19. This is in marked contrast to the tens of thousands of deaths reported in many higher-income countries. The true extent of COVID-19 in the community was unknown and likely to be higher than reports indicated. Uyoga <jats:italic>et al.</jats:italic> found an overall seroprevalence among blood donors of 4.3%, peaking in 35- to 44-year-old individuals (see the Perspective by Maeda and Nkengasong). The low mortality can be partly explained by the steep demographics in Kenya, where less than 4% of the population is 65 or older. These circumstances combine to result in Kenyan hospitals not currently being overwhelmed by patients with respiratory distress. However, the imposition of a strict lockdown in this country has shifted the disease burden to maternal and child deaths as a result of disruption to essential medical services. </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="6524" page="79" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abe1916">79</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6524" page="27" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abf8832">27</jats:related-article> </jats:p>

<jats:title>Aerosols give clouds a lift</jats:title> <jats:p>It has been observed that atmospheric aerosols can strengthen updrafts in deep convective clouds such as those that form in thunderstorms. Past work has linked such invigoration with the latent heat released by water condensation or freezing in chains of processes that depend on aerosol concentrations. Abbott and Cronin suggest a third possibility in which updrafts intensify because high aerosol concentrations increase environmental humidity by mixing more condensed water into the surrounding air, which in turn favors stronger updrafts.</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="6524" page="83" related-article-type="in-this-issue" vol="371" xlink:href="10.1126/science.abc5181">83</jats:related-article> </jats:p>

<jats:p>Metamorphic proteins switch between different folds, defying the protein folding paradigm. It is unclear how fold switching arises during evolution. With ancestral reconstruction and nuclear magnetic resonance, we studied the evolution of the metamorphic human protein XCL1, which has two distinct folds with different functions, making it an unusual member of the chemokine family, whose members generally adopt one conserved fold. XCL1 evolved from an ancestor with the chemokine fold. Evolution of a dimer interface, changes in structural constraints and molecular strain, and alteration of intramolecular protein contacts drove the evolution of metamorphosis. Then, XCL1 likely evolved to preferentially populate the noncanonical fold before reaching its modern-day near-equal population of folds. These discoveries illuminate how one sequence has evolved to encode multiple structures, revealing principles for protein design and engineering.</jats:p>