Catálogo de publicaciones - revistas

<jats:title>Diversity in ion channel complexes</jats:title> <jats:p> AMPA receptors are glutamate activated ion channels that mediate fast synaptic transmission in the nervous system and play a key role in learning and memory. The receptors are tetramers built from various combinations of four subunits, with functional diversity coming from the range of subunit compositions. Zhao <jats:italic>et al.</jats:italic> purified native receptors from rat brains and determined the structures of 10 different complexes by cryo–electron microscopy. Certain arrangements of the four subunits are preferred. The structure of a key gating element—a linker between the transmembrane and ligand binding domains—reveals how this receptor may function. </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="6438" page="355" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw8250">355</jats:related-article> </jats:p>

<jats:title>Creation of the splicing catalytic center</jats:title> <jats:p> The catalytic center of the fully assembled, precatalytic pre–B spliceosome is not yet formed, even though all the pieces are present in this complex. Charenton <jats:italic>et al.</jats:italic> solved the structures of the human pre–B complex, providing detailed mechanistic insights into how the helicase Prp28 transfers the 5′ splice site of the messenger RNA precursor from U1 small nuclear ribonucleoprotein (snRNP) to U6 snRNA. The pairing of the 5′ splice site with U6 induces a series of conformational changes that triggers the relocation of Brr2 helicase and loading of U4 snRNA to the helicase active site. This leads to unwinding of the U4/U6 snRNA duplex and allows U6 to fold and pair with U2 to create the spliceosome active site. </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="6438" page="362" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aax3289">362</jats:related-article> </jats:p>

<jats:title>Good vibrations in quantum communication</jats:title> <jats:p> Quantum information processing platforms typically require qubits to talk to each other. To date, photons (either optical or microwave) have been the carrier of choice to transfer quantum states between the qubits. For some solid-state systems, however, the vibrational properties of the materials themselves, phonons, could be advantageous. Bienfait <jats:italic>et al.</jats:italic> describe the deterministic emission and capture of itinerant phonons through an acoustic communication channel, enabling the phonon-based coherent transfer of quantum states from one superconducting qubit to another and the quantum entanglement of the two qubits over the acoustic channel. The results provide a route to couple hybrid quantum solid-state systems using surface acoustic waves. </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="6438" page="368" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw8415">368</jats:related-article> </jats:p>

<jats:title>Easy ice removal</jats:title> <jats:p> The accumulation of ice on a surface can lead to hazardous conditions, such as on the surface of an airplane wing or the side of a tall building. Ice adhesion, even to a surface treated to minimize the bonded force, will usually depend on the amount of surface coverage. Golovin <jats:italic>et al.</jats:italic> compared strength-limited deicing with toughness-limited deicing. Whereas normal deicing materials focus on minimizing the adhesion strength, the authors show that if a material is designed with low-adhesion toughness, deicing is no longer a function of the coverage area. </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="6438" page="371" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aav1266">371</jats:related-article> </jats:p>

<jats:title>Graphite gets a second sound</jats:title> <jats:p> Between the two extremes of ballistic and diffusive lattice thermal transport is the potential for an exotic wave-like state known as second sound. Huberman <jats:italic>et al.</jats:italic> used fast, transient thermal grating measurements to show the existence of second sound in graphite between 85 and 125 kelvin (see the Perspective by Shi). Previous observations of second sound have been rare, confined to isotopically pure materials at very low temperatures. The observation of second sound in graphite is likely due to its layered nature, suggesting that this thermal transport mode may be accessible in other two-dimensional materials. </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="6438" page="375" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aav3548">375</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6438" page="332" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aax2319">332</jats:related-article> </jats:p>

<jats:title>Atom scattering reveals bond formation</jats:title> <jats:p> When molecules collide, they can form an addition complex in which new chemical bonds can form. However, if energy does not flow out of this complex and into the rest of the molecule, the new bond will usually simply dissociate. Jiang <jats:italic>et al.</jats:italic> observed the scattering of hydrogen atoms from graphene and interpreted their results with a first-principles potential energy surface and a dynamical simulation (see the Perspective by Hornekaer). At near-normal incidence, these experiments probe transient carbon-hydrogen bond formation when the hydrogen atoms collide with the centers of the six-atom carbon rings. Rapid intramolecular vibrational relaxation results from orbital rehybridization and structural deformations that occur during bond formation. </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="6438" page="379" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw6378">379</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6438" page="331" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aax1980">331</jats:related-article> </jats:p>

<jats:title>Sulfur tells tectonic secrets</jats:title> <jats:p> Plate tectonics dominates how the surface of Earth is shaped over geologic time; however, we do not know when this important process started on Earth. Smit <jats:italic>et al.</jats:italic> used sulfur isotopes in diamonds to show that atmospheric sulfur was entering the mantle 3 billion years ago through plate subduction. Older diamonds do not have this signature, constraining when plate tectonics started on Earth to around 3 billion years ago. </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="6438" page="383" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw9548">383</jats:related-article> </jats:p>

<jats:title>Circulation more than temperature</jats:title> <jats:p> Changes in continental configuration and sea level affected the ocean's oxygen levels and the rate of denitrification between 70 and 30 million years ago. That finding by Kast <jats:italic>et al.</jats:italic> shows a fundamental difference from the modern ocean, in which the extent of suboxia is controlled primarily by global temperature. Changes in the nitrogen isotopic composition of marine organic matter correlate with the collision of India and Asia and the circulation changes that occurred as a result. Later, isotopic composition changed further in response to a fall in sea level as global cooling caused ice sheets to grow. </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="6438" page="386" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aau5784">386</jats:related-article> </jats:p>

<jats:title>The architecture of a signaling hub</jats:title> <jats:p> Adenylyl cyclases (ACs) respond to a variety of inputs to generate the signaling molecule cyclic adenosine monophosphate. ACs are regulated by G proteins, which are activated by upstream receptors. Qi <jats:italic>et al.</jats:italic> determined the structure of bovine membrane AC9 bound to an activated G protein αs subunit by cryo–electron microscopy at 3.4-angstrom resolution. The structure provides the full architecture of AC9, including a helical domain that connects the transmembrane and catalytic domains. The model reveals how the domains interact to regulate enzymatic activity, including suggesting a mechanism of self-inhibition. </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="6438" page="389" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aav0778">389</jats:related-article> </jats:p>

<jats:title>A new protein channel family</jats:title> <jats:p> Exposure of cells to acidic conditions outside the cell activates chloride-conducting channels that influence physiological and pathological processes. Yang <jats:italic>et al.</jats:italic> used an unbiased RNA interference screen to identify the channel protein that allows such proton-activated ion conductance. The protein, called PAC for proton-activated channel, has two predicted transmembrane domains and is unlike any previously identified channel. Identification of the channel should advance studies of its physiological roles, which range from tissue injury after stroke to adaptation of Tibetan natives to a high-altitude environment. </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="6438" page="395" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aav9739">395</jats:related-article> </jats:p>