Catálogo de publicaciones - revistas

<jats:p>High-resolution structures of folding intermediates of proteins come into view.</jats:p>

<jats:title>Biodiversity Convention</jats:title> <jats:p> In October 2010, the Convention on Biological Diversity will meet to assess the current condition of global biodiversity and to propose and agree on priorities for its future conservation. In this context, <jats:bold> Rands <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1298" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1189138">1298</jats:related-article> ; see the <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5997" page="1272" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.2010.329.5997.329_1272">News Focus section</jats:related-article> ; see the cover) review recent patterns of biodiversity conservation, highlighting successes, as well as current and future threats. They argue that biodiversity should be treated as a public good, with responsibility for its conservation integrated across sectors of society and government, rather than be confined to the business of environmental agencies, and review the conditions under which this goal might be achieved. </jats:p>

<jats:p>An asteroid follows the orbit of the planet Neptune in a region of gravitational stability.</jats:p>

<jats:p>Einstein@Home, a distributed computing project, discovered a rare, isolated pulsar with a low magnetic field.</jats:p>

<jats:title>The Root of the Problem</jats:title> <jats:p> Developmental processes can define repeated patterns of structure, such as somites in vertebrates. In plants, too, repeated structures arise during growth and development. As the above-ground shoot grows, it sends out leaves or branches at intervals guided by hormone signaling. As the below-ground root grows, it too ramifies, sending out lateral roots. <jats:bold> Moreno-Risueno <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1306" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191937">1306</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5997" page="1290" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1195572">Traas and Vernoux</jats:related-article> </jats:bold> ) explored the expression of genes underlying development of lateral roots and found that oscillations in gene expression guide the specification of lateral roots. </jats:p>

<jats:title>Transient Protein Conformations</jats:title> <jats:p> Transient conformations are important to protein function; however, detecting and characterizing these states is technically challenging. <jats:bold> Korzhnev <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1312" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191723">1312</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="5997" page="1295" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1195571"> <jats:bold>Al-Hashimi</jats:bold> </jats:related-article> ) combined recently developed methods to determine the three-dimensional atomic-resolution structure of a transient intermediate of a four-helix bundle protein domain. The intermediate formed rapidly but, owing to structural peculiarities, slowly rearranged into its native state. The methods can be applied not only to folding intermediates but also to excited states important for protein function. </jats:p>

<jats:title>High-Temperature Electronic Switching</jats:title> <jats:p> In electronic circuitry, the band gap of a semi-conductor helps to provide the barrier that keeps charge carriers from flowing until a voltage is applied that switches the device. As temperatures rise, the carriers acquire enough thermal energy to overcome the band gap, causing the device to leak current even when they are turned off. The higher band gap of silicon carbide (SiC) makes it an attractive candidate for higher-temperature operations compared to conventional silicon, but several performance issues occur with SiC junction field-effect transistors. <jats:bold> T.-H. Lee <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1316" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192511">1316</jats:related-article> ) describe the fabrication of SiC nano-electromechanical switches that formed inverter circuits with extremely low leakage currents and switched billions of times at 500°C. </jats:p>

<jats:title>Chlorophyll Sees Red</jats:title> <jats:p> Among the first facts students learn about the natural world is that plants owe their green color to the pigment chlorophyll. There have actually been a handful of slightly different chlorophyll variants uncovered over the years, and <jats:bold> Chen <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1318" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1191127">1318</jats:related-article> , published online 19 August) have found another in bacteria from Shark Bay, Australia. The chlorophyll variant displayed a red-shifted absorption spectrum, which extended into the near-infrared region due to the insertion of a formyl group on the molecule's periphery. The precise cellular function of the pigment awaits further study. </jats:p>

<jats:title>Oscillations in Carbon Nanotube Conductivity</jats:title> <jats:p> Theoretical studies have suggested that protons can be conducted rapidly in water trapped inside carbon nanotubes. <jats:bold> C. Y. Lee <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1320" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1193383">1320</jats:related-article> ) connected two aqueous reservoirs with opened, single-walled carbon nanotubes, half a millimeter long but only 1.5 nanometers wide, and observed a high, stable proton current under electroosmotic conditions arising from a single nanotube. The addition of alkali cations caused random pore blocking and oscillations in ion current, resembling events seen in biological ion channels. </jats:p>

<jats:title>Charging Back and Forth</jats:title> <jats:p> Ion binding by proteins can exert a major influence on electron transfer events in biological systems. <jats:bold> Park <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1324" related-article-type="in-this-issue" vol="329" xlink:href="10.1126/science.1192044">1324</jats:related-article> ) discovered an analogous phenomenon in a simpler synthetic system. Specifically, a certain flexible molecule, known as a calix[4]pyrrole derivative, adopts a conical conformation upon binding anions, such as chloride or bromide, and this in turn leads to electron transfer to a guest acceptor that drifts into the cone. Addition of a cation that fitted more snugly into the conical cavity resulted in a reversal of the electron transfer reaction. The whole process was mapped out by spectroscopic and crystallographic characterization of the intermediates and products. </jats:p>