Catálogo de publicaciones - revistas

<jats:title>Visualizing superexchange interactions</jats:title> <jats:p> The resolution that can be achieved in scanning probe microscopy can be greatly enhanced by absorbing a molecule such as CO on the probe tip. Czap <jats:italic>et al.</jats:italic> now show that this approach can be used to scan spin and magnetic properties of molecules on a surface. They adsorbed a magnetic molecule, Ni(cyclopentadienyl) <jats:sub>2</jats:sub> , on a silver surface and then transferred one of these molecules to a scanning tunnel microscope tip. They could then bring the tip toward the adsorbate-covered surface and map out the strength of superexchange interactions. </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="6441" page="670" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw7505">670</jats:related-article> </jats:p>

<jats:title>Sweet spot for making oligosaccharides</jats:title> <jats:p> Sugars pose a challenge for chemists: how to string together functional group–rich building blocks that can adopt multiple conformations. Two papers in this issue used sugar building blocks constrained by a macrocyclic linker to encourage formation of a specific glycosidic linkage (see the Perspective by Pohl). Ikuta <jats:italic>et al.</jats:italic> used glucose building blocks containing a linker that changes the sugar conformation to synthesize cyclic oligomers with only three or four units. The linker changes the conformation of the glucose monomers, enabling them to come together despite the strain in the final structure. Komura <jats:italic>et al.</jats:italic> prepared sialic acid building blocks with a linker that allows for selective formation of the α-anomeric linkage with a range of nucleophiles. They synthesized dimers of sialic acid with many different linkages and a pentamer with four α(2,8) linkages. This method enabled chemical synthesis of components of mammalian glycans involved in brain development, cell adhesion, and immune response. </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="6441" page="674" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw3053">674</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6441" page="677" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw4866">677</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6441" page="631" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aax3501">631</jats:related-article> </jats:p>

<jats:title>Sweet spot for making oligosaccharides</jats:title> <jats:p> Sugars pose a challenge for chemists: how to string together functional group–rich building blocks that can adopt multiple conformations. Two papers in this issue used sugar building blocks constrained by a macrocyclic linker to encourage formation of a specific glycosidic linkage (see the Perspective by Pohl). Ikuta <jats:italic>et al.</jats:italic> used glucose building blocks containing a linker that changes the sugar conformation to synthesize cyclic oligomers with only three or four units. The linker changes the conformation of the glucose monomers, enabling them to come together despite the strain in the final structure. Komura <jats:italic>et al.</jats:italic> prepared sialic acid building blocks with a linker that allows for selective formation of the α-anomeric linkage with a range of nucleophiles. They synthesized dimers of sialic acid with many different linkages and a pentamer with four α(2,8) linkages. This method enabled chemical synthesis of components of mammalian glycans involved in brain development, cell adhesion, and immune response. </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="6441" page="674" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw3053">674</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6441" page="677" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw4866">677</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6441" page="631" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aax3501">631</jats:related-article> </jats:p>

<jats:title>Excising an olefin</jats:title> <jats:p> Plants produce an abundance of structurally complex terpene compounds that are useful precursors to pharmaceuticals and other fine chemicals. However, the carbon frameworks of these compounds constrain the available pathways for diversification. Smaligo <jats:italic>et al.</jats:italic> now show that successive treatment with ozone, an iron oxidant, and a hydrogen-atom donor can cleanly cleave pendant olefins from terpenes and related compounds (see the Perspective by Caille). Breaking the bond between saturated and double-bonded carbon centers offers a direct route to desirable chiral intermediates from readily available, inexpensive precursors. </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="6441" page="681" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aaw4212">681</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6441" page="635" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aax2613">635</jats:related-article> </jats:p>

<jats:title>Brain cell transcriptomes in autism</jats:title> <jats:p> Autism manifests in many ways. Despite that diversity, the disorder seems to affect specific cellular pathways, including those observed in the neocortex of patients' brains. Velmeshev <jats:italic>et al.</jats:italic> analyzed the transcriptomes of single brain cells, including neurons and glia, from patients with autism. Single-nucleus RNA sequencing analysis suggested that affected pathways regulate synapse function as well as neural outgrowth and migration. Furthermore, in patient samples, specific sets of genes enriched in upper-layer projection neurons and microglia correlated with clinical severity. </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="6441" page="685" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aav8130">685</jats:related-article> </jats:p>

<jats:title>Transport control</jats:title> <jats:p> The membrane protein P-glycoprotein protects cells by using energy from adenosine triphosphate (ATP) hydrolysis to expel chemical substances, including drugs. Inhibiting P-glycoprotein may thus ameliorate drug resistance. Structures of P-glycoprotein in the apo state and bound to substrate and inhibitor give insight into the transport mechanism, but a full picture requires access to substates in the transport cycle. Dastvan <jats:italic>et al.</jats:italic> used double electron electron resonance spectroscopy to show that substrates enhance transport by stabilizing an asymmetric post–ATP-hydrolysis state. By contrast, inhibitors stabilize a symmetric state that impairs transport. </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="6441" page="689" related-article-type="in-this-issue" vol="364" xlink:href="10.1126/science.aav9406">689</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>RNA is not a “plain” molecule–it is replete with various chemical modifications. Just how many types of modifications exist, where they are located, and what they do is becoming clearer, as researchers hone the tools to examine such questions at the transcriptome-wide level.</jats:p>