Catálogo de publicaciones - revistas

<jats:title>An RNA methylase caught in the act</jats:title> <jats:p> RNA methylation is important in RNA function and in antibiotic resistance. The RNA methylase RlmN is a dual-specificity enzyme that can act on ribosomal and transfer RNA (tRNA). RlmN is a radical S-adenosylmethionine (SAM) enzyme, which produces a protein/RNA cross-linked intermediate. Schwalm <jats:italic>et al.</jats:italic> determined the structure of RlmN cross-linked to a tRNA substrate and found that the enzyme recognizes the overall shape of the tRNA. Then it remodels the anticodon region to access the base that it methylates. The remodeling activity is likely to be key to the enzyme's dual specificity. </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="6283" page="309" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad5367">309</jats:related-article> </jats:p>

<jats:title>Cassini detects interstellar dust grains</jats:title> <jats:p> The interstellar medium contains an array of small solid particles known as dust grains. Altobelli <jats:italic>et al.</jats:italic> used the dust analyzer on the Cassini probe to detect 36 interstellar dust grains as they passed by Saturn, and they measured the grains' elemental abundances. The results show that, remarkably, these grains lack carbon-bearing compounds and have been homogenized in the interstellar medium into silicates with iron inclusions. </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="6283" page="312" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aac6397">312</jats:related-article> </jats:p>

<jats:title>Stable magnets from single atoms</jats:title> <jats:p> An important goal in molecular magnetism is to create a permanent magnet from a single atom. Metal atoms adsorbed on surfaces can develop strong magnetization in an applied field (paramagnetism). Donati <jats:italic>et al.</jats:italic> show that single holmium atoms adsorbed on a magnesium oxide film grown on a silver substrate show residual magnetism for temperatures up to 30 K and bistabilty that lasts for 1500 s at 10 K (see the Perspective by Khajetoorians and Heinrich). The atom avoids spin relaxation by a combination of quantum-state symmetry and by the oxide film preventing the spin from interacting with the underlying metal via tunneling. </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="6283" page="318" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad9898">318</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6283" page="296" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf2481">296</jats:related-article> </jats:p>

<jats:title>Quantum effects in single hydrogen bonds</jats:title> <jats:p> Hydrogen bonds are a combination of electrostatics with a nuclear quantum contribution arising from the light mass of hydrogen nuclei. However, the quantum states of hydrogen nuclei are extremely sensitive to coupling with local environments, and these effects are broadened and averaged with conventional spectroscopic or diffraction techniques. Guo <jats:italic>et al.</jats:italic> show that quantum effects change the strength of individual hydrogen bonds in water layers adsorbed on a salt surface. These effects are revealed in inelastic tunneling spectra obtained with a chlorine-terminated scanning tunneling microscope tip. </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="6283" page="321" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf2042">321</jats:related-article> </jats:p>

<jats:title>Making a teeny tiny engine</jats:title> <jats:p> Steam locomotives, cars, and the drinking bird toy all convert heat into useful work as it cycles between two reservoirs at different temperatures. Usually, the working substance where the heat-work conversion occurs is a liquid or a gas, consisting of many molecules. Roβnagel <jats:italic>et al.</jats:italic> have made a working substance of a single calcium ion in a tapered ion trap. A laser-cooling beam plays the part of a cold reservoir for the calcium ion, and in turn, electric field noise acts as a hot reservoir. </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="6283" page="325" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad6320">325</jats:related-article> </jats:p>

<jats:title>Where Pd and B meet in Suzuki coupling</jats:title> <jats:p>The Suzuki-Miyaura reaction is widely used to form carbon-carbon bonds. It operates by transferring a carbon center from boron to palladium, although the handoff itself happens too quickly to see. Thomas and Denmark have caught sight of the previously elusive intermediate complexes linking palladium to boron through an intervening oxygen. Using low-temperature nuclear magnetic resonance spectroscopy, they characterized the intermediate structures just before the carbon transfer event.</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="6283" page="329" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aad6981">329</jats:related-article> </jats:p>

<jats:title>Modulating metal oxides</jats:title> <jats:p> The more difficult step in fuel cells and water electrolysis is the oxygen evolution reaction. The search for earth-abundant materials to replace noble metals for this reaction often turns to oxides of three-dimensional metals such as iron. Zhang <jats:italic>et al.</jats:italic> show that the applied voltages needed to drive this reaction are reduced for iron-cobalt oxides by the addition of tungsten. The addition of tungsten favorably modulates the electronic structure of the oxyhydroxide. A key development is to keep the metals well mixed and avoid the formation of separate phases. </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="6283" page="333" related-article-type="in-this-issue" vol="352" xlink:href="10.1126/science.aaf1525">333</jats:related-article> </jats:p>