Catálogo de publicaciones - revistas

<jats:title>Three strands ironed closely together</jats:title> <jats:p> It is not uncommon when braiding hair or bread to intertwine three different strands. At the molecular level, however, synthetic knots have thus far been restricted to architectures accessible from two-strand braids. Danon <jats:italic>et al.</jats:italic> used iron ion coordination to guide three organic ligand strands to form a knot geometry with eight separate crossings. </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="6321" page="159" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aal1619">159</jats:related-article> </jats:p>

<jats:title>A cyclic catalyst to pair up sugars</jats:title> <jats:p> Linking sugar molecules together to make complex carbohydrates is a geometrical challenge. For a six-carbon sugar such as glucose, there are six different possible linkage sites and also two possible configurations in which to anchor the incipient bond. Park <jats:italic>et al.</jats:italic> developed a ring-shaped, dimeric catalyst that pairs sugars after one of them has been modified with a chloride. The thiourea-based catalyst appears to pull away the chloride while simultaneously activating the incoming second sugar. The resultant bond-forming process reliably inverts the initial C–Cl configuration. </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="6321" page="162" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aal1875">162</jats:related-article> </jats:p>

<jats:title>Pin the tail on the hydrogens</jats:title> <jats:p> X-ray diffraction has been the method of choice for determining the positions of atoms within a crystal. However, the technique works better for atoms with higher atomic numbers and requires single crystals of a minimum size. Palatinus <jats:italic>et al.</jats:italic> used electron diffraction, a technique of increasing importance for analyzing very small crystals, to identify the positions of hydrogen atoms in organic and inorganic materials (see the Perspective by McCusker). </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="6321" page="166" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aak9652">166</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6321" page="136" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aal4570">136</jats:related-article> </jats:p>

<jats:title>Redox metabolite role in biofilms</jats:title> <jats:p> In the microbial world, the chemical diversity of secreted metabolites is vast, and their physiological roles are underexplored. Costa <jats:italic>et al.</jats:italic> studied the redox-active secondary metabolite pyocyanin, which is produced by the opportunistic pathogen <jats:italic>Pseudomonas aeruginosa.</jats:italic> Pyocyanin mediates the generation of thick biofilms containing extracellular DNA that are important in pathogenesis. The authors characterized the demethylase PodA, which catalyzes the conversion of pyocyanin to hydroxyphenazine and deranges biofilm formation. PodA could represent a therapeutic lead for intractable bacterial infections. </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="6321" page="170" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aag3180">170</jats:related-article> </jats:p>

<jats:title>Soil biota and plant diversity</jats:title> <jats:p> Soil biota, including symbionts such as mycorrhizal fungi and nitrogen-fixing bacteria, as well as fungal and bacterial pathogens, affect terrestrial plant diversity and growth patterns (see the Perspective by van der Putten). Teste <jats:italic>et al.</jats:italic> monitored growth and survival in Australian shrubland plant species paired with soil biota from plants of the same species and from other plants that use different nutrient acquisition strategies. Plant-soil feedbacks appear to drive local plant diversity through interactions between the different types of plants and their associated soil biota. Bennett <jats:italic>et al.</jats:italic> studied plant-soil feedbacks in soil and seeds from 550 populations of 55 species of North American trees. Feedbacks ranged from positive to negative, depending on the type of mycorrhizal association, and were related to how densely the same species occurred in natural populations. </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="6321" page="134" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aal4549">134</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6321" page="173" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aai8291">173</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6321" page="181" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aai8212">181</jats:related-article> </jats:p>

<jats:title>How to get to place B</jats:title> <jats:p> We constantly navigate around our environment. This means moving from our current location, place A, to a new goal, place B. We have recently learned much about spatial maps in the brain in which place cells indicate current location. However, it is unclear how navigational goals are represented in the brain. Sarel <jats:italic>et al.</jats:italic> describe a group of neurons in the brains of bats that are tuned to goal direction and distance relative to the bat's current position as it flies toward its goal. The finding elucidates the computations involved in spatial navigation. </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="6321" page="176" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aak9589">176</jats:related-article> </jats:p>

<jats:title>Soil biota and plant diversity</jats:title> <jats:p> Soil biota, including symbionts such as mycorrhizal fungi and nitrogen-fixing bacteria, as well as fungal and bacterial pathogens, affect terrestrial plant diversity and growth patterns (see the Perspective by van der Putten). Teste <jats:italic>et al.</jats:italic> monitored growth and survival in Australian shrubland plant species paired with soil biota from plants of the same species and from other plants that use different nutrient acquisition strategies. Plant-soil feedbacks appear to drive local plant diversity through interactions between the different types of plants and their associated soil biota. Bennett <jats:italic>et al.</jats:italic> studied plant-soil feedbacks in soil and seeds from 550 populations of 55 species of North American trees. Feedbacks ranged from positive to negative, depending on the type of mycorrhizal association, and were related to how densely the same species occurred in natural populations. </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="6321" page="134" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aal4549">134</jats:related-article> , p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6321" page="173" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aai8291">173</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6321" page="181" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aai8212">181</jats:related-article> </jats:p>

<jats:title>Parallel computation in memory-making</jats:title> <jats:p> The hippocampus plays a central role in the encoding, consolidation, and recall of memories. Consolidation and recall are thought to be executed by the replay of previously acquired memory traces by hippocampal cell assemblies. The hippocampus is thus considered to be the initiator of memory redistribution processes. However, O'Neill <jats:italic>et al.</jats:italic> now report that the superficial layers of the medial entorhinal cortex show replay events that are independent of hippocampal activity (see the Perspective by Moser and Gardner). Computations in memory systems may thus be organized in a less hierarchical, more parallel way than previously thought. </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="6321" page="184" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aag2787">184</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6321" page="131" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aam5404">131</jats:related-article> </jats:p>

<jats:title>Are you aware how well you remember?</jats:title> <jats:p> Self-monitoring and evaluation of our own memory is a mental process called metamemory. For metamemory, we need access to information about the strength of our own memory traces. The brain structures and neural mechanisms involved in metamemory are completely unknown. Miyamoto <jats:italic>et al.</jats:italic> devised a test paradigm for metamemory in macaques, in which the monkeys judged their own confidence in remembering past experiences. The authors combined this approach with functional brain imaging to reveal the neural substrates of metamemory for retrospection. A specific region in the prefrontal brain was essential for meta mnemonic decision-making. Inactivation of this region caused selective impairment of metamemory, but not of memory itself. </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="6321" page="188" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aal0162">188</jats:related-article> </jats:p>

<jats:title>Phages build themselves a wall</jats:title> <jats:p> The compartmentalization of DNA replication away from other cytoplasmic events is a key feature of the cell nucleus. Chaikeeratisak <jats:italic>et al.</jats:italic> studied the replication of the very large <jats:italic>Pseudomonas</jats:italic> bacteriophage 201φ2-1 by using fluorescence microscopy and cryo–electron tomography. They found that the phage assembled a nucleus-like compartment when it infected a bacterial cell. The phage genome was completely enclosed by an apparently contiguous protein shell, within which DNA replication, recombination, and transcription occurred. Translation, precursor biosynthesis, and viral assembly occurred outside the structure. </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="6321" page="194" related-article-type="in-this-issue" vol="355" xlink:href="10.1126/science.aal2130">194</jats:related-article> </jats:p>