Catálogo de publicaciones - revistas

<jats:title>Prokaryotic enzymes for viral defense</jats:title> <jats:p> The arms race between prokaryotes and viruses provides a strong evolutionary force to create diverse enzymatic activities that mediate antiviral immune responses. These immune components often cluster together in the host genomes, leading to expanded defense systems. Taking advantage of the evolutionary modularity of defense systems, Gao <jats:italic>et al.</jats:italic> bioinformatically predicted defense genes in most available bacterial and archaeal genomes. In addition, they reconstituted the newly identified systems in Escherichia coli and verified their defense functions against specific bacteriophages. In particular, they characterized defense functions for several predicted nucleoside triphosphatases. </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="6507" page="1077" related-article-type="in-this-issue" vol="369" xlink:href="10.1126/science.aba0372">1077</jats:related-article> </jats:p>

<jats:title>Twelve-qubit quantum computing for chemistry</jats:title> <jats:p> Accurate electronic structure calculations are considered one of the most anticipated applications of quantum computing that will revolutionize theoretical chemistry and other related fields. Using the Google Sycamore quantum processor, Google AI Quantum and collaborators performed a variational quantum eigensolver (VQE) simulation of two intermediate-scale chemistry problems: the binding energy of hydrogen chains (as large as H <jats:sub>12</jats:sub> ) and the isomerization mechanism of diazene (see the Perspective by Yuan). The simulations were performed on up to 12 qubits, involving up to 72 two-qubit gates, and show that it is possible to achieve chemical accuracy when VQE is combined with error mitigation strategies. The key building blocks of the proposed VQE algorithm are potentially scalable to larger systems that cannot be simulated classically. </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="6507" page="1084" related-article-type="in-this-issue" vol="369" xlink:href="10.1126/science.abb9811">1084</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6507" page="1054" related-article-type="in-this-issue" vol="369" xlink:href="10.1126/science.abd3880">1054</jats:related-article> </jats:p>

<jats:title>Plant cell wall construction crew</jats:title> <jats:p> Plants produce a complex cell wall in which cellulose, a glucose polymer, is a major component. Cellulose fibers are formed from close-packed single chains of cellulose that have been proposed to be formed by multimeric complexes (18 or more subunits) of the enzyme cellulose synthase, which exists in several isoforms. Purushotham <jats:italic>et al.</jats:italic> determined a cryo–electron microscopy structure of a trimer of a single isoform of cellulose synthase. A large channel forms a path for cellulose chains through the membrane-embedded complex. The structure also reveals oligomeric interfaces and provides a framework for modeling the larger complexes seen in plant membranes. The close arrangement of exit sites for nascent glycan chains is consistent with the enzyme complex playing a role in directing cellulose microfibril 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="6507" page="1089" related-article-type="in-this-issue" vol="369" xlink:href="10.1126/science.abb2978">1089</jats:related-article> </jats:p>

<jats:title>Soil sulfur metabolism surprise</jats:title> <jats:p> Soil bacteria have a range of metabolic pathways that contribute to acquiring and recycling nutrients and carbon. Curiously, some of these organisms give off ethylene gas when starved for sulfur under anaerobic conditions. North <jats:italic>et al.</jats:italic> traced the source of ethylene to a small, sulfur-containing organic molecule produced by certain reactions in cells. Growing cells in sulfur-limiting conditions enabled them to identify the enzymes involved in sulfur salvage, and the concomitant ethylene production, through this pathway. Methane and ethane were also observed as products when appropriate substrates were provided. The key genes involved are distantly related to nitrogenase and several other reductase enzymes found in bacteria and archaea. The involvement of such nitrogenase-like genes in sulfur metabolism highlights the potential of unexplored diversity in this family of enzymes and raises many mechanistic and evolutionary questions that are now ripe for exploration. </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="6507" page="1094" related-article-type="in-this-issue" vol="369" xlink:href="10.1126/science.abb6310">1094</jats:related-article> </jats:p>