Catálogo de publicaciones - revistas

<jats:title>A human P spliceosome structure</jats:title> <jats:p> Splicing of some pre–messenger RNAs could be regulated by cell type–specific splicing factors. Fica <jats:italic>et al.</jats:italic> describe the cryo–electron microscopy structure of the human postcatalytic (P) spliceosome. Surprisingly, it lacks the splicing factor Prp18, which plays an essential role in exon ligation in the yeast spliceosome. Instead, a metazoan-specific splicing factor, FAM32A, compensates for Prp18 and promotes exon ligation by penetrating the active sites and directly stapling the 5′ exon and the 3′ splice site. These findings suggest a way to control tissue-specific alternative splicing. </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="6428" page="710" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw5569">710</jats:related-article> </jats:p>

<jats:title>A path through a crowd</jats:title> <jats:p> Catalytic reactions on surfaces occur at pressures at which the surfaces are completely covered with adsorbed molecules. It would seem that this arrangement would interfere with reactants encountering one another through diffusion processes. Henß <jats:italic>et al.</jats:italic> used high-speed scanning tunneling microscopy to follow the diffusion of oxygen atoms on a ruthenium surface that was fully covered with carbon monoxide (CO) molecules (see the Perspective by Magnussen). Oxygen-atom diffusion was unexpectedly fast. A theoretical model revealed that CO diffusion appears to open pathways for oxygen-atom movement. </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="6428" page="715" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav4143">715</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6428" page="695" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw4900">695</jats:related-article> </jats:p>

<jats:title>Low-power organic transistors</jats:title> <jats:p> For internet-of-things applications, transistors that deliver high signal amplification (high gain) at low power will help conserve power and extend battery life. Jiang <jats:italic>et al.</jats:italic> used inkjet printing to fabricate an organic transistor in which silver metal contacts form a low Schottky barrier (less than 0.2 electron volt) with an organic semiconductor. The transistor delivered gain near the theoretical limit at a power below 1 nanowatt and detected electrophysiological signals from the skin with a wearable device. </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="6428" page="719" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav7057">719</jats:related-article> </jats:p>

<jats:title>Elastic ceramics</jats:title> <jats:p> Aerogels hold promise as lightweight replacements for thermal insulation. However, poor mechanical stability has hampered progress in moving toward commercialization. Xu <jats:italic>et al.</jats:italic> designed a mechanical metamaterial that pinches in a small amount when you compress it (see the Perspective by Chhowalla and Jariwala). This is characteristic of materials with a negative Poisson's ratio and dramatically improves mechanical stability. The trick was using three-dimensional graphene structures to template the ceramic aerogels, thus producing a superinsulating material endowed with excellent mechanical 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="6428" page="723" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav7304">723</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6428" page="694" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw5670">694</jats:related-article> </jats:p>

<jats:title>An integrated route to quantum detection</jats:title> <jats:p> The quantum properties of the nitrogen-vacancy (NV) center defect in diamond are being pursued as building blocks for quantum-enhanced technologies. Addressing and manipulating the defects, however, typically requires bulk optics, which could limit scalability. Siyushev <jats:italic>et al.</jats:italic> developed an on-chip technique in which the NV center is detected optoelectronically. Such a detection and manipulation method offers a route to develop an integrated platform for scalable quantum-based sensing technologies. </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="6428" page="728" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav2789">728</jats:related-article> </jats:p>

<jats:title>Cluster isomerization</jats:title> <jats:p> Structural rearrangements at the atomic scale can range from isomerization of small molecules to solid-solid phase transformations of crystals. Williamson <jats:italic>et al.</jats:italic> show that magic-size cadmium sulfide (CdS) crystalline clusters, which are about 2 nanometers in diameter and expose a large fraction of surface atoms capped by bidentate oleate ligands, undergo a reversible isomerization. The initial α-Cd <jats:sub>37</jats:sub> S <jats:sub>20</jats:sub> phase, which has a wurtzite-like crystal structure, isomerizes to β-Cd <jats:sub>37</jats:sub> S <jats:sub>20</jats:sub> , which has a zinc blende–like structure upon exposure to methanol, and then transforms back under vacuum. This transition is driven by distortion of the ligand shell and shifts the excitonic energy gap of the clusters. </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="6428" page="731" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau9464">731</jats:related-article> </jats:p>

<jats:title>Inferring blocked mantle convection</jats:title> <jats:p> The boundaries between rocks with different physical properties in Earth's interior come from either a change in crystal structure or a change in chemical composition. Wu <jats:italic>et al.</jats:italic> examined the roughness of the boundary between Earth's upper and lower mantle, thought to form from a change in mineral structure (see the Perspective by Houser). To their surprise, in some locations, the boundary has small-scale roughness that requires some chemical difference above and below the boundary. This observation provides evidence of partially blocked mantle circulation that leads to some chemical differences between the upper and lower mantle. </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="6428" page="736" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav0822">736</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6428" page="696" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw4601">696</jats:related-article> </jats:p>

<jats:title>Mechanism of ribosome rescue</jats:title> <jats:p> Bacterial ribosomes that stall on truncated or cleaved messenger RNA (mRNA) are rescued by trans-translation. Two factors, transfer-messenger RNA (tmRNA) and small protein B (SmpB), resolve the stalled complex by tagging the nascent polypeptide for degradation and facilitating release of the ribosome. Rae <jats:italic>et al.</jats:italic> determined structures of key trans-translation intermediates. The structures reveal how SmpB identifies stalled ribosomes; how the large, circularized tmRNA molecule moves through the ribosome; and how translation is shifted from the truncated mRNA to tmRNA. </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="6428" page="740" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav9370">740</jats:related-article> </jats:p>

<jats:title>Getting over nucleosomal barriers</jats:title> <jats:p> In eukaryotic cells, RNA polymerase II (RNAPII) transcribes DNA within nucleosome-coated chromatin. The nucleosomes can provide major roadblocks for transcription. Cells solve this problem by using transcription elongation factors. Ehara <jats:italic>et al.</jats:italic> solved the cryo–electron microscopy structures of the nucleosome-transcribing RNAPII with elongation factors Elf1 and Spt4/5. Elf1 and Spt4/5 cooperatively suppress RNAPII pausing at multiple super helical locations [SHL(−6), SHL(−5), and SHL(−2)] and facilitate RNAPII progression through SHL(−1) by adjusting the nucleosome position to favor forward progression. </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="6428" page="744" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav8912">744</jats:related-article> </jats:p>

<jats:title>B1 or B2? The BCR decides</jats:title> <jats:p> Immunological B cells are generally divided into two major subsets. B2 cells generate specific antibodies against foreign antigens in secondary lymphoid organs. B1 cells, found predominantly in the peritoneal and pleural cavities, instead produce “natural” antibodies as part of the innate immune system. Two models to explain this split exist: the “lineage model,” wherein both subsets have distinct progenitors, and the “selection model,” in which fates are directed by different B cell antigen receptors (BCRs). Graf <jats:italic>et al.</jats:italic> provide support for the selection model using a transgenic system in which BCR specificities can be changed. Mature B2 cells differentiated into functional B1 cells when a self-reactive B1 BCR was swapped in, in the absence of B1 lineage precommitment. </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="6428" page="748" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau8475">748</jats:related-article> </jats:p>