Catálogo de publicaciones - revistas

<jats:title>Structural basis for spliceosome assembly</jats:title> <jats:p> The spliceosome removes noncoding sequences from precursor RNA and ligates coding sequences into useful mRNA. The pre-spliceosome (A complex) associates with a small nuclear ribonucleoprotein (snRNP) complex called U4/U6.U5 tri-snRNP to form the pre-B complex, which is converted into the precatalytic B complex. Bai <jats:italic>et al.</jats:italic> solved the cryo–electron microscopy structures of the pre-B and B complexes isolated from yeast. These structures show the U1 and U2 snRNPs and allow modeling of the A complex to reveal the early steps of spliceosome assembly and activation. </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="6396" page="1423" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aau0325">1423</jats:related-article> </jats:p>

<jats:title>Going beyond the first Chern number</jats:title> <jats:p> Topological properties of physical systems are reflected in so-called Chern numbers: A nonzero Chern number typically means that a system is topologically nontrivial. Sugawa <jats:italic>et al.</jats:italic> engineered a cold atom system with a nonzero second Chern number, in contrast to condensed matter physics, where only the first Chern number is usually invoked. The exotic topology relates to the emergence of a type of magnetic monopole called the Yang monopole (known from theoretical high-energy physics) in a five-dimensional space of internal degrees of freedom in a rubidium Bose-Einstein condensate. The results illustrate the potential of cold atoms physics to simulate high-energy phenomena. </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="6396" page="1429" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aam9031">1429</jats:related-article> </jats:p>

<jats:title>A brush with friction</jats:title> <jats:p> Polyelectrolyte brushes consist of charged polymer chains attached to a common backbone or surface. They provide excellent lubrication between two surfaces for both engineered and physiological materials. The packing of the brushes is sensitive to pH, temperature, or added salts. Yu <jats:italic>et al.</jats:italic> show that the presence of multivalent ions can cause brush collapse, similarly to monovalent ions (see the Perspective by Ballauff). Critically—and not observed with the addition of monovalent ions—very low concentrations of multivalent ions cause bridging between the brushes and increase friction between the surfaces to the extent that their value for biomedical devices is limited. </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="6396" page="1434" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aar5877">1434</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6396" page="1399" related-article-type="in-this-issue" vol="360" xlink:href="10.1126/science.aat5343">1399</jats:related-article> </jats:p>