Catálogo de publicaciones - revistas

<jats:title>Five-membered rings for two nickels</jats:title> <jats:p>The Diels-Alder reaction is widely used to make six-membered rings by adding four-carbon dienes to two-carbon alkenes. It would seem straightforward to likewise access five-membered rings from dienes and one-carbon sources, or carbenes, but that does not tend to work. Instead, the carbene adds to just half of the diene to form a cyclopropane. Zhou and Uyeda now show that a catalyst with two nickel centers can steer this reaction toward the cyclopentyl products (see the Perspective by Johnson and Weix). A chiral version of the catalyst rendered the reaction enantioselective in intramolecular cases.</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="6429" page="857" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau0364">857</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6429" page="819" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw5825">819</jats:related-article> </jats:p>

<jats:title>Two timelines for extinction</jats:title> <jats:p> The Cretaceous-Paleogene extinction that wiped out the nonavian dinosaurs 66 million years ago was correlated with two extreme events: The Chicxulub impact occurred at roughly the same time that massive amounts of lava were erupting from the Deccan Traps (see the Perspective by Burgess). Sprain <jats:italic>et al.</jats:italic> used argon-argon dating of the volcanic ash from the Deccan Traps to argue that a steady eruption of the flood basalts mostly occurred after the Chicxulub impact. Schoene <jats:italic>et al.</jats:italic> used uranium-lead dating of zircons from ash beds and concluded that four large magmatic pulses occurred during the flood basalt eruption, the first of which preceded the Chicxulub impact. Whatever the correct ordering of events, better constraints on the timing and rates of the eruption will help elucidate how volcanic gas influenced climate. </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="6429" page="866" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav1446">866</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6429" page="862" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau2422">862</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6429" page="815" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw0473">815</jats:related-article> </jats:p>

<jats:title>Two timelines for extinction</jats:title> <jats:p> The Cretaceous-Paleogene extinction that wiped out the nonavian dinosaurs 66 million years ago was correlated with two extreme events: The Chicxulub impact occurred at roughly the same time that massive amounts of lava were erupting from the Deccan Traps (see the Perspective by Burgess). Sprain <jats:italic>et al.</jats:italic> used argon-argon dating of the volcanic ash from the Deccan Traps to argue that a steady eruption of the flood basalts mostly occurred after the Chicxulub impact. Schoene <jats:italic>et al.</jats:italic> used uranium-lead dating of zircons from ash beds and concluded that four large magmatic pulses occurred during the flood basalt eruption, the first of which preceded the Chicxulub impact. Whatever the correct ordering of events, better constraints on the timing and rates of the eruption will help elucidate how volcanic gas influenced climate. </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="6429" page="866" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav1446">866</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6429" page="862" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aau2422">862</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6429" page="815" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw0473">815</jats:related-article> </jats:p>

<jats:title>Harnessing self-tuned strain</jats:title> <jats:p> Strain can modify the electronic properties of a metal and has provided a method for enhancing electrocatalytic activity. For practical catalysts, nanomaterials with high surface areas are needed. However, for nanoparticles, strain is often induced with overlayers (adsorbates or heteroatoms) that can undergo reconstruction during operation that releases the induced strain. Wang <jats:italic>et al.</jats:italic> show that freestanding palladium nanosheets (three to five monolayers thick) form with an internal compressive strain of 1 to 2% and can be much more active for both the oxygen and hydrogen evolution reactions under alkaline conditions compared with nanoparticles. </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="6429" page="870" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aat8051">870</jats:related-article> </jats:p>

<jats:title>A key to potassium channel activation</jats:title> <jats:p> Using drugs to activate potassium channels has the potential to treat conditions like epilepsy, heart arrhythmias, and pain. Schewe <jats:italic>et al.</jats:italic> report a class of negatively charged activators (NCAs) with a defined pharmacore that use a similar mechanism to activate many types of potassium channels. X-ray crystallography, functional analysis, and molecular dynamics simulations showed that the NCAs bind below the selectivity filter to open the filter gate and activate the channels. Targeting this NCA site might be exploited in rational drug design. </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="6429" page="875" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav0569">875</jats:related-article> </jats:p>

<jats:title>Sleep may protect the brain from AD</jats:title> <jats:p> Two main proteins accumulate in the brain in Alzheimer's disease (AD), β-amyloid (Aβ) and tau. Aβ appears to instigate AD, but tau appears to drive brain damage and cognitive decline. Sleep deprivation is known to increase Aβ acutely and chronically. Now, Holth <jats:italic>et al.</jats:italic> show that chronic sleep deprivation strongly increases tau acutely over hours and also drives tau pathology spreading in the brains of mice and humans (see the Perspective by Noble and Spires-Jones). Thus, sleep appears to have a direct protective effect on a key protein that drives AD pathology. </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="6429" page="880" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aav2546">880</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6429" page="813" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aaw5583">813</jats:related-article> </jats:p>

<jats:title>Expanding the genetic code</jats:title> <jats:p> DNA and RNA are naturally composed of four nucleotide bases that form hydrogen bonds in order to pair. Hoshika <jats:italic>et al.</jats:italic> added an additional four synthetic nucleotides to produce an eight-letter genetic code and generate so-called hachimoji DNA. Coupled with an engineered T7 RNA polymerase, this expanded DNA alphabet could be transcribed into RNA. Thus, new forms of DNA that add information density to genetic biopolymers can be generated that may be useful for future synthetic biological applications. </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="6429" page="884" related-article-type="in-this-issue" vol="363" xlink:href="10.1126/science.aat0971">884</jats:related-article> </jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>

<jats:p>Biomarkers for neurological diseases used to be few and far between, but better technology is making it easier for researchers to track brain health by measuring molecules. This means less invasive testing, earlier diagnosis, faster drug development, and—hopefully—more effective treatments.</jats:p>