Catálogo de publicaciones - revistas

<jats:title>Understanding splicing from the 3′ end</jats:title> <jats:p> The spliceosome removes introns from eukaryotic mRNA precursors and yields mature transcripts by joining exons. Despite decades of functional studies and recent progress in understanding the spliceosome structure, the mechanism by which the 3′ splice site (SS) is recognized by the spliceosome has remained unclear. Liu <jats:italic>et al.</jats:italic> and Wilkinson <jats:italic>et al.</jats:italic> report the high-resolution cryo-electron microscopy structures of the yeast postcatalytic spliceosome. The structures reveal that the 3′SS is recognized through non-Watson-Crick base pairing with the 5′SS and the branch point, stabilized by the intron region and protein factors. </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="6368" page="1278" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aar3462">1278</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6368" page="1283" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aar3729">1283</jats:related-article> </jats:p>

<jats:title>Understanding splicing from the 3′ end</jats:title> <jats:p> The spliceosome removes introns from eukaryotic mRNA precursors and yields mature transcripts by joining exons. Despite decades of functional studies and recent progress in understanding the spliceosome structure, the mechanism by which the 3′ splice site (SS) is recognized by the spliceosome has remained unclear. Liu <jats:italic>et al.</jats:italic> and Wilkinson <jats:italic>et al.</jats:italic> report the high-resolution cryo-electron microscopy structures of the yeast postcatalytic spliceosome. The structures reveal that the 3′SS is recognized through non-Watson-Crick base pairing with the 5′SS and the branch point, stabilized by the intron region and protein factors. </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="6368" page="1278" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aar3462">1278</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6368" page="1283" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aar3729">1283</jats:related-article> </jats:p>

<jats:title>Clocking departures from chiral origins</jats:title> <jats:p> Just as the atoms in a molecule can be arranged in a left- or right-handed manner, the field in a beam of light can circulate like a left- or right-handed corkscrew. Matches or mismatches in this mutual handedness give rise to an asymmetric distribution of trajectories as electrons are ejected during photoionization. Beaulieu <jats:italic>et al.</jats:italic> used an interferometric approach to uncover the temporal dynamics associated with this asymmetry. They probed the mirror-image isomers of camphor with circularly polarized light, which revealed the angle-dependent delays between trajectories that spanned up to 24 attoseconds. </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="6368" page="1288" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aao5624">1288</jats:related-article> </jats:p>

<jats:title>Many roads to being tough</jats:title> <jats:p> A number of routes exist to increase toughness in both natural and human-made materials—for example, using secondary phases and precipitates or exploiting tailored architectures and shaped crystals. Polishchuk <jats:italic>et al.</jats:italic> detail the nanoscale internal structure of calcitic microlenses formed by a brittlestar (see the Perspective by Duffy). The segregation of magnesium-rich particles forms a secondary phase that places compressive stresses on the host matrix. This toughening mechanism resembles Guinier-Preston zones known in classical metallurgy. </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="6368" page="1294" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aaj2156">1294</jats:related-article> see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6368" page="1254" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aaq0111">1254</jats:related-article> </jats:p>

<jats:title>Conditions in a black hole outburst</jats:title> <jats:p> The binary system V404 Cygni consists of a red giant star orbiting a black hole. In 2015, a surge of accretion by the black hole caused the surrounding plasma to brighten suddenly for the first time since 1989, briefly becoming the brightest x-ray source in the sky. Dallilar <jats:italic>et al.</jats:italic> combined observations from radio, infrared, optical, and x-ray telescopes taken during the outburst. They compared how fast the flux decayed at each wavelength, which allowed them to constrain the size of the emitting region, determine that the plasma within it cooled through synchrotron radiation, and measure the magnetic field around the black hole. </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="6368" page="1299" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aan0249">1299</jats:related-article> </jats:p>

<jats:title>Watching electrons lose steam in graphene</jats:title> <jats:p> Although graphene can be fabricated to be extremely clean, it still has a nonzero electrical resistance. Resistance is associated with turning electrons' energy into heat, but how exactly does this happen? Halbertal <jats:italic>et al.</jats:italic> used a tiny scanning temperature probe based on a superconducting quantum interference device to investigate this problem. As the current flowed through a square-shaped sample of graphene, electrons lost energy predominantly in the vicinity of atomic-scale defects, which were few and far between in the bulk but much more common on the edges of the sample. </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="6368" page="1303" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aan0877">1303</jats:related-article> </jats:p>

<jats:title>A sweet source to make acrylonitrile</jats:title> <jats:p> Much of the attention directed toward displacing petroleum feedstocks with biomass has focused on fuels. However, there are also numerous opportunities in commodity chemical production. One such candidate is acrylonitrile, a precursor to a wide variety of plastics and fibers that is currently derived from propylene. Karp <jats:italic>et al.</jats:italic> efficiently manufactured this compound from an ester (ethyl 3-hydroxypropanoate) that can be sourced renewably from sugars. The process relies on inexpensive titania as a catalyst and avoids the side production of cyanide that accompanies propylene oxidation. </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="6368" page="1307" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aan1059">1307</jats:related-article> </jats:p>

<jats:title>A magnetic tip reconfigures edge states</jats:title> <jats:p> Topological phases of matter are characterized by invariants such as Chern numbers, which determine their global properties. On the boundary of two domains with different Chern numbers, chiral edge states are expected to form. Yasuda <jats:italic>et al.</jats:italic> engineered such states in samples of a quantum anomalous Hall material by creating magnetic domains using the tip of a magnetic force microscope. The existence of chiral edge states along the domain walls was confirmed with electrical transport measurements. The ability to reconfigure and manipulate these states may improve spintronics. </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="6368" page="1311" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aan5991">1311</jats:related-article> </jats:p>

<jats:title>Probing an excitonic condensate</jats:title> <jats:p> Excitons—bound states of electrons and holes in solids—are expected to form a Bose condensate at sufficiently low temperatures. Excitonic condensation has been studied in systems such as quantum Hall bilayers where physical separation between electrons and holes enables a longer lifetime for their bound states. Kogar <jats:italic>et al.</jats:italic> observed excitons condensing in the three-dimensional semimetal 1 <jats:italic>T</jats:italic> -TiSe <jats:sub>2</jats:sub> . In such systems, distinguishing exciton condensation from other types of order is tricky. To do so, the authors used momentum-resolved electron energy-loss spectroscopy, a technique developed to probe electronic collective excitations. The energy needed to excite an electronic mode became negligible at a finite momentum, signifying the formation of a condensate. </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="6368" page="1314" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aam6432">1314</jats:related-article> </jats:p>

<jats:title>Building a brain</jats:title> <jats:p> The human brain is built in an inside-out manner as a series of layers. Although progenitor cells spin off new neurons in a seemingly organized fashion, the devil is in the details. Nowakowski <jats:italic>et al.</jats:italic> analyzed the transcriptomes of single cells from the developing brain to elucidate the hidden complexity of brain construction. For each cell, its position within the brain matters, as well as what type of neuron is being made at what point during overall development. These individual expression patterns result in organized diversity in the brain's cortex. </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="6368" page="1318" related-article-type="in-this-issue" vol="358" xlink:href="10.1126/science.aap8809">1318</jats:related-article> </jats:p>