Catálogo de publicaciones - revistas

<jats:p>Metabolic engineering has the potential to produce from simple, readily available, inexpensive starting materials a large number of chemicals that are currently derived from nonrenewable resources or limited natural resources. Microbial production of natural products has been achieved by transferring product-specific enzymes or entire metabolic pathways from rare or genetically intractable organisms to those that can be readily engineered, and production of unnatural specialty chemicals, bulk chemicals, and fuels has been enabled by combining enzymes or pathways from different hosts into a single microorganism and by engineering enzymes to have new function. Whereas existing production routes use well-known, safe, industrial microorganisms, future production schemes may include designer cells that are tailor-made for the desired chemical and production process. In any future, metabolic engineering will soon rival and potentially eclipse synthetic organic chemistry.</jats:p>

<jats:title>Reading, Writing, and Face Recognition</jats:title> <jats:p> Reading, not to mention writing and texting, is a relatively recent invention, and hence it is believed that a preliterate brain must adapt on the fly, so to speak, in learning how to process written words, rather than being able to rely upon evolutionarily ancient modifications of the visual system pathways. <jats:bold> Dehaene <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="1359" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194140">1359</jats:related-article> , published online 11 November) examined the neural response to a range of visual stimuli in three groups: illiterate adults, adults who learned to read as children, and adults who learned to read as adults. Reading induced a greater facility in processing horizontally oriented stimuli at early stages in the visual pathway and was also associated with the appearance of an area specialized for words. This gain of function appeared to occur at a cost—the area in the temporal cortex devoted to face processing shrank. </jats:p>

<jats:title>Shake It to Wake It</jats:title> <jats:p> Viscoelastic materials combine the recoverable stretchiness found in elastic materials with the slow-flowing behavior of a thick fluid, like honey. When subjected to an oscillatory motion, the response will depend on the frequency. At low frequencies, the viscous behavior will dominate and lead to a dissipation of the applied energy as heat, while at fast frequencies the elastic behavior dominates. <jats:bold> Xu <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="1364" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194865">1364</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="6009" page="1332" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1198982">Gogotsi</jats:related-article> </jats:bold> ) developed a viscoelastic material with an exceptionally broad operating temperature range, based on a network of carbon nanotubes. The responsiveness of the material was probably caused by the “zipping” and “unzipping” of the nanotubes at points of contact. </jats:p>

<jats:title>Skin-Deep Raman Spectroscopy</jats:title> <jats:p> Raman spectroscopy allows for molecular identification via vibrational spectra at optical wavelengths. However, if the optical signal is scattered, as occurs when trying to image tissue, the signal becomes very weak, and it becomes difficult to image a sample with high time resolution. <jats:bold> Saar <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="1368" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197236">1368</jats:related-article> ) now show that by improving the optics and electronics of the acquisition of the backscattered signal, stimulated Raman scattering spectroscopy can be performed at video rates on human skin, which should enable label-free studies of tissues and, for example, the tracking of the delivery of a drug. </jats:p>

<jats:title>An Upside of Asymmetry</jats:title> <jats:p> Advances in synthetic techniques have enabled the preparation of nanometer-scale semiconductors in a wide range of precise shapes and sizes, including core-shell morphologies that layer several different materials in the same particle. Such two-in-one motifs are promising for light-harvesting applications because they allow optically induced charge separation across the internal interface. <jats:bold> Borys <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="1371" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1198070">1371</jats:related-article> ) studied a series of rod-shaped cadmium sulfide–cadmium selenide hybrid particles using single-particle–resolved optical spectroscopy and found that smooth versus bulbous geometries produced distinct emission spectra. Further analysis of more complex, tetrapodal particles (with four arms aligned tetrahedrally) suggested that nonuniform geometries facilitate interfacial charge transfer by reducing the likelihood of electronic band misalignment. </jats:p>

<jats:title>Cryptic Sulfur Cycling</jats:title> <jats:p> Aerobic bacteria and ocean circulation patterns control the formation and distribution of oxygen-minimum zones at moderate depth in the oceans. These habitats host microorganisms that thrive on other metabolic substrates in the absence of oxygen—most commonly, metabolizing thermodynamically favorable nitrogen compounds like nitrate. Off the coast of Chile, however, <jats:bold> Canfield <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="1375" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1196889">1375</jats:related-article> , published online 11 November; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6009" page="1326" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1198400">Teske</jats:related-article> </jats:bold> ) suggest that bacteria may often reduce sulfate as well. Metagenomic sequencing revealed the presence of both sulfate-reducing and sulfide-oxidizing bacteria. With the coincidence of sulfate and nitrate reduction, the sulfur and nitrogen cycles may be intimately linked; for example, sulfate reduction could provide nitrogen-rich ammonium for bacteria that ultimately transform it into nitrogen gas. </jats:p>

<jats:title>Sunny and Cool</jats:title> <jats:p> Changes in solar output cause changes in the amount of radiation that Earth receives from the Sun, which in turn can cause climate variations. The effects of solar variations are not uniform over the globe—owing to the complexity of the climate system, larger solar fluxes may produce warming in one area but cooling in another. <jats:bold> Marchitto <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="1378" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194887">1378</jats:related-article> ) present a record of Holocene sea surface temperature in the eastern equatorial Pacific Ocean that shows cooling as solar output increased and warming as the Sun dimmed. These temperature changes resulted from dynamical control of El Niño and La Niña episodes by solar radiative forcing of Earth's climate. </jats:p>

<jats:title>Ocean Dweller Sequenced</jats:title> <jats:p> The Tunicates, which include the solitary free-swimming larvaceans that are a major pelagic component of our oceans, are a basal lineage of the chordates. In order to investigate the major evolutionary transition represented by these organisms, <jats:bold> Denoeud <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="1381" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194167">1381</jats:related-article> , published online 18 November) sequenced the genome of <jats:italic>Oikopleura dioica</jats:italic> , a chordate placed by phylogeny between vertebrates and amphioxus. Surprisingly, the genome showed little conservation in genome architecture when compared to the genomes of other animals. Furthermore, this highly compacted genome contained intron gains and losses, as well as species-specific gene duplications and losses that may be associated with development. Thus, contrary to popular belief, global similarities of genome architecture from sponges to humans are not essential for the preservation of ancestral morphologies. </jats:p>

<jats:title>DNA Damage Pathways Revealed</jats:title> <jats:p> Despite the dynamic nature of cellular responses, the genetic networks that govern these responses have been mapped primarily as static snapshots. <jats:bold> Bandyopadhyay <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="1385" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1195618">1385</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="6009" page="1327" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1199862">Friedman and Schuldiner</jats:related-article> </jats:bold> ) report a comparison of large genetic interactomes measured among all yeast kinases, phosphatases, and transcription factors, as the cell responded to DNA damage. The interactomes revealed were highly dynamic structures that changed dramatically with changing conditions. These dynamic interactions reveal genetic relationships that can be more effective than classical “static” interactions (for example, synthetic lethals and epistasis maps) in identifying pathways of interest. </jats:p>

<jats:title>Deadly Trio</jats:title> <jats:p> The proteins BAX and BAK act as a key decision point, regulating apoptosis by controlling the permeability of the mitochondrial outer membrane. Evidence has been presented for two mechanisms of activation of BAX and BAK: an indirect mechanism where proapoptotic proteins neutralize the antiapoptotic effects of the protein BCL-2 and its relatives; or direct activation of BAX and BAK by BIM, BID, or PUMA. Analysis of the situation in vivo is complicated by the overlapping function of BIM, BID, and PUMA. <jats:bold> Ren <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="1390" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1190217">1390</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="6009" page="1330" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1199461">Martin</jats:related-article> </jats:bold> ) thus analyzed triple-knockout mice lacking BIM, BID, and PUMA. Apoptosis during mouse development required a direct effect of one of these proteins to activate BAX or BAK, thereby promoting cell death. </jats:p>