Catálogo de publicaciones - revistas

<jats:title>DNA bricks build nanotube transistors</jats:title> <jats:p> Semiconducting carbon nanotubes (CNTs) are an attractive platform for field-effect transistors (FETs) because they potentially can outperform silicon as dimensions shrink. Challenges to achieving superior performance include creating highly aligned and dense arrays of nanotubes as well as removing coatings that increase contact resistance. Sun <jats:italic>et al.</jats:italic> aligned CNTs by wrapping them with single-stranded DNA handles and binding them into DNA origami bricks that formed an array of channels with precise intertube pitches as small as 10.4 nanometers. Zhao <jats:italic>et al.</jats:italic> then constructed single and multichannel FETs by attaching the arrays to a polymer-templated silicon wafer. After adding metal contacts across the CNTs to fix them to the substrate, they washed away all of the DNA and then deposited electrodes and gate dielectrics. The FETs showed high on-state performance and fast on-off switching. </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="6493" page="874" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz7440">874</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6493" page="878" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aaz7435">878</jats:related-article> </jats:p>

<jats:title>Bumble bee gardeners</jats:title> <jats:p> Bumble bees rely heavily on pollen resources for essential nutrients as they build their summer colonies. Therefore, we might expect that annual differences in the availability of these resources must simply be tolerated, but Pashalidou <jats:italic>et al.</jats:italic> made observations suggesting that bees may have strategies to cope with irregular seasonal flowering (see the Perspective by Chittka). When faced with a shortage of pollen, bumble bees actively damaged plant leaves in a characteristic way, and this behavior resulted in earlier flowering by as much as 30 days. Experimenters were not able to fully replicate the results with their own damage, suggesting that there is a distinct method that the bees use to stimulate earlier flowering. </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="6493" page="881" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aay0496">881</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6493" page="824" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abc2451">824</jats:related-article> </jats:p>

<jats:title>Electronic and nuclear dynamics in one</jats:title> <jats:p> Because of the complex, ultrafast interplay between nuclear and electronic degrees of freedom, probing both nuclear and electronic dynamics in excited electronic states within a single time-resolved experiment is a great challenge. Yang <jats:italic>et al.</jats:italic> used ultrafast electron diffraction in combination with ab initio nonadiabatic molecular dynamics and diffraction simulations to study the relaxation dynamics of isolated pyridine molecules after photoexcitation to the S <jats:sub>1</jats:sub> state (see the Perspective by Domcke and Sobolewski). They showed that electronic state evolution and molecular structural changes can be recorded simultaneously and independently by tracing a transient signal in small-angle inelastic scattering and large-angle elastic diffraction, respectively. </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="6493" page="885" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb2235">885</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6493" page="820" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb9937">820</jats:related-article> </jats:p>

<jats:title>Good timing for microwave technology</jats:title> <jats:p> Timing standards around the world define the second using atomic clocks, specifically the microwave frequencies emitted from trapped atoms. Optical clocks, which are based on optical transitions of atoms, operate at much higher frequency and have been shown to exhibit better stability. Nakamura <jats:italic>et al.</jats:italic> demonstrate a framework that carries the improved stability of the optical domain over to microwaves (see the Perspective by Curtis). In addition to contributing to the eventual redefinition of the second based on optical clocks, this work will also lead to improvements in microwave-based technologies such as astronomical imaging and geodesy through very long baseline interferometry, radar, communications, and navigation systems. </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="6493" page="889" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb2473">889</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6493" page="825" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.abb8629">825</jats:related-article> </jats:p>

<jats:title>Transport dependent on context</jats:title> <jats:p> Transporter proteins move substrates across a membrane, often coupling this activity to cellular ion concentration gradients. For neurotransmitter transporters, which reside in synaptic vesicles that fuse with the plasma membrane after an action potential, transport activity needs to be regulated so that they do not pump out neurotransmitters after vesicle fusion. Using cryo–electron microscopy, Li <jats:italic>et al.</jats:italic> determined the structure of a vesicular glutamate transporter from rat that unveils some of the distinctive features that enable it to function properly in two distinct cellular environments. An allosteric pH sensor, proposed to be a glutamate residue, gates binding of the substrate glutamate and simultaneously permits binding and counterflow of chloride ions. This molecular traffic light allows for a single ion channel to behave appropriately in different contexts. </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="6493" page="893" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aba9202">893</jats:related-article> </jats:p>

<jats:title>Supramolecular attack particles</jats:title> <jats:p> Cytotoxic T cells (CTLs) are at the front lines against cancer and chronic infection. T cells kill by secreting caspase-activating granzymes and the pore-forming protein perforin from dense core granules. However, the structural basis of lethal hit delivery has remained unknown. Balint <jats:italic>et al.</jats:italic> enriched the synaptic output of CTLs to investigate the released form of perforin and granzyme B. They found that CTLs released perforin and granzymes in stable particles called supramolecular attack complexes or SMAPs. The SMAPs were composed of a core shell structure and were assembled in the CTL dense secretory granules before release. The released SMAPs showed an innate ability to kill target 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="6493" page="897" related-article-type="in-this-issue" vol="368" xlink:href="10.1126/science.aay9207">897</jats:related-article> </jats:p>