Catálogo de publicaciones - revistas

<jats:title>Teasing out chirality in graphene</jats:title> <jats:p> A chiral elementary particle has its spin pointing in either the same or the opposite direction as its momentum. In graphene, electrons have an analogous chirality, but observing it in electrical transport experiments is tricky. To do this, Wallbank <jats:italic>et al.</jats:italic> studied how electrons tunnel between two slightly misaligned graphene sheets separated by a layer of insulating hexagonal boron nitride. The chiral nature of the electrons imposed restrictions on the tunneling, which made it possible to discern the signatures of chirality in the data. </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="6299" page="575" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf4621">575</jats:related-article> </jats:p>

<jats:title>Flood control initiates Chinese civilization</jats:title> <jats:p> Around four millennia ago, Emperor Yu the Great succeeded in controlling a huge flood in the Yellow River basin. This is considered to have led to the establishment of the Xia dynasty and the start of Chinese civilization. However, the dates of the events and the links between them have remained uncertain and controversial. Using stratigraphic data and radiocarbon dating, Wu <jats:italic>et al.</jats:italic> verify that the flood occurred and place the start of the Xia dynasty at about 1900 BC, thus reconciling the historical and archaeological chronologies (see the Perspective by Montgomery). </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="6299" page="579" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf0842">579</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6299" page="538" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aah4040">538</jats:related-article> </jats:p>

<jats:title>Xenobiotics to the rescue</jats:title> <jats:p> Contaminating microorganisms can be highly detrimental to the large-scale fermentation of complex low-cost feedstocks, such as sugarcane or dry-milled corn for biofuels or other industrial purposes. The challenge is that foreign organisms have to be inhibited without using antibiotics because of concerns about spreading antibiotic resistance. Shaw <jats:italic>et al.</jats:italic> engineered bacteria and yeast to use rare compounds as sources of nutrients (see the Perspective by Lennen). Engineering the common biocatalyst <jats:italic>Escherichia coli</jats:italic> , for example, to consume melamine as a nitrogen source allowed it to outcompete contaminating organisms. Similarly, engineering yeast to use cyanamide for nitrogen or phosphite for phosphorus also improved competitive fitness. </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="6299" page="583" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf6159">583</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6299" page="542" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aah4106">542</jats:related-article> </jats:p>

<jats:title>Searching for the Sun</jats:title> <jats:p> The growth of immature sunflower plants tracks the Sun's movement. The young plants lean westward as the day progresses but reorient to the east each night. As the flowers mature and open, they settle into a stable east-facing orientation. Atamian <jats:italic>et al.</jats:italic> show how circadian rhythms regulate the east-west elongation of cells in the young plants' stems (see the Perspective by Briggs). They show that eastward-oriented flowers are warmer than westward-oriented flowers, and this warmth attracts pollinators. Auxin signaling pathways in the stem coordinate to fix the eastward orientation of the mature plant. </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="6299" page="587" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf9793">587</jats:related-article> ; see also p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6299" page="541" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aah4439">541</jats:related-article> </jats:p>

<jats:p>Many organisms form elaborate mineralized structures, constituted of highly organized arrangements of crystals and organic macromolecules. The localization of crystals within these structures is presumably determined by the interaction of nucleating macromolecules with the mineral phase. Here we show that, preceding nucleation, a specific interaction between soluble organic molecules and an organic backbone structure directs mineral components to specific sites. This strategy underlies the formation of coccoliths, which are highly ordered arrangements of calcite crystals produced by marine microalgae. On combining the insoluble organic coccolith scaffold with coccolith-associated soluble macromolecules in vitro, we found a massive accretion of calcium ions at the sites where the crystals form in vivo. The in vitro process exhibits profound similarities to the initial stages of coccolith biogenesis in vivo.</jats:p>

<jats:title>Insights into proteasome inhibition</jats:title> <jats:p> Proteasomes are large protein complexes that degrade and remove proteins to maintain proper cellular physiology and growth. Proteasomes are a validated target for anticancer therapy, but drug design has been hampered by poor understanding of how inhibitors interact with the active site. Schrader <jats:italic>et al.</jats:italic> succeeded in crystallizing various proteasome-inhibitor complexes. They subsequently obtained crystal structures for the native human proteasome and eight different inhibitor complexes at resolutions between 1.9 and 2.1 Å. The inhibitors sampled include drugs that are approved or in trial for cancer treatment. </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="6299" page="594" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf8993">594</jats:related-article> </jats:p>

<jats:title>Spatial organization inside the nucleus</jats:title> <jats:p> In eukaryotic cells, DNA is packaged into a complex macromolecular structure called chromatin. Wang <jats:italic>et al.</jats:italic> have developed an imaging method to map the position of multiple regions on individual chromosomes, and the results confirm that chromatin is organized into large contact domains called TADS (topologically associating domains). Unexpectedly, though, folding deviates from the classical fractal-globule model at large length scales. </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="6299" page="598" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf8084">598</jats:related-article> </jats:p>

<jats:title>Axonal pathology and necroptosis in ALS</jats:title> <jats:p> Necroptosis, a non–caspase-dependent form of cell death, can be reduced in disease states by inhibiting a kinase called RIPK1. Until now, no human mutations have been linked to necroptosis. Ito <jats:italic>et al.</jats:italic> show that loss of optineurin, which is encoded by a gene that has been implicated in the human neurodegenerative disorder ALS (amyotrophic lateral sclerosis), results in sensitivity to necroptosis and axonal degeneration. When RIPK1-kinase dependent signaling is disrupted in mice that lack optineurin, necroptosis is inhibited and axonal pathology is reversed. </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="6299" page="603" related-article-type="in-this-issue" vol="353" xlink:href="10.1126/science.aaf6803">603</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>