Catálogo de publicaciones - revistas

<jats:p>Three distantly-related mammals share a brain architecture characterized by a density of π</jats:p>

<jats:title>Common Themes</jats:title> <jats:p> Both plants and animals need to be able to distinguish between their own tissues and the cells and tissues of an invading pathogen. Across kingdoms there exists a range of pattern recognition systems that have become integral to the evolution of innate immune responses. <jats:bold>Ronald and Beutler</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1061" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1189468">1061</jats:related-article> ) synthesize recent intellectual progress to bring insights into shared features of animal immunology and plant pathology. </jats:p>

<jats:p>Mutations causing a rare skin disease reveal a signaling pathway that is a drug target for Alzheimer’s disease.</jats:p>

<jats:title>Regulating Migration</jats:title> <jats:p> The migration of cells around the body is an important factor in cancer development and the establishment of infection. Movement is induced by small proteins called chemokines, and so for a specific function, migration is controlled by a relevant chemokine binding to its respective receptor. This family of receptors is known as guanine (G) protein–coupled receptors, which span cell membranes to mediate between external signals from chemokines and internal mechanisms. The chemokine receptor CXCR4 is implicated in many types of cancer and in infection, and <jats:bold> Wu <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="1066" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194396">1066</jats:related-article> , published online 7 October; see the Report by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6007" page="1091" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197410"> Chien <jats:italic>et al.</jats:italic> </jats:related-article> </jats:bold> ) report on a series of crystal structures obtained for CXCR4 bound to small molecules. In every case, the same homodimer structure was observed, suggesting that the interface is functionally relevant. These structures offer insights into the interactions between CXCR4 and its natural chemokine, as well as with the virus HIV-1. </jats:p>

<jats:title>Quantum Connection</jats:title> <jats:p> A system that is quantum mechanically entangled with another distant system can be predicted by measuring the distant system. This form of “action-at-a-distance,” or nonlocality, seemingly contradicts Heisenberg's uncertainty principle, which is one of the fundamental aspects of quantum mechanics. <jats:bold>Oppenheim and Wehner</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="1072" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1192065">1072</jats:related-article> ) show that the degree of nonlocality in quantum mechanics is actually determined by the uncertainty principle. The unexpected connection between nonlocality and uncertainty holds true for other physical theories besides quantum mechanics. </jats:p>

<jats:title>Speeding Electron Transfer Between Proteins</jats:title> <jats:p> Compared to those observed in photosynthetic proteins, electron transfer rates between other large biomolecules, such as myoglobin and cytochrome b <jats:sub>5</jats:sub> , are very slow. <jats:bold> Xiong <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="1075" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1197054">1075</jats:related-article> ) show that modifying the acidic amino acid residues in the binding surface of myoglobin to lysine changes the distribution of structures to ones that favor faster electron transfer from the zinc porphyrin in myoglobin to the heme iron of cytochrome b <jats:sub>5</jats:sub> . The rates observed are within an order of magnitude of those observed for the initial step of charge separation in photosynthesis and provide valuable data for scientists interested in designing reactive proteins. </jats:p>

<jats:title>Finely Tracking Flow</jats:title> <jats:p> Magnetic resonance imaging (MRI) is in principle well-suited for tracking flow dynamics in microfluidic channels. However, multiple channels tend to be arrayed on much larger substrates, and MRI coils large enough to enclose the whole assembly do not have the sensitivity required to resolve an intimate picture of any one channel. <jats:bold> Bajaj <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="1078" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1192313">1078</jats:related-article> , published online 7 October; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6007" page="1056" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1198402"> <jats:bold>Utz and Landers</jats:bold> </jats:related-article> ) present an imaging protocol in which the spins of the fluid molecules in a microfluidic chip are first tagged by a conventionally sized coil and then analyzed downstream using a more sensitive and smaller coil through which the fluid flows incrementally after leaving the microfluidic device. </jats:p>

<jats:title>Enhanced Strain Sensitivity</jats:title> <jats:p> The ability to measure tiny deformations in length is useful for many disciplines, from largescale structural engineering to DNA analysis with optical tweezers. The most sensitive strain sensors are those using optical interferometers, which can detect small changes at the scale of visible wavelengths. Using an optical frequency comb to stabilize the output of a diode laser, and as a highly accurate ruler to determine small changes in length of an optic fiber sensor, <jats:bold> Gagliardi <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="1081" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1195818">1081</jats:related-article> , published online 28 October) showed that sensitivity can be enhanced by several orders of magnitude. Such combined technology should provide for a new generation of high-performance sensors. </jats:p>

<jats:title>Moving Carbon</jats:title> <jats:p> During the last glacial maximum, approximately 23,000 years ago, both the atmosphere and the terrestrial biosphere contained much less carbon than in the immediately preindustrial era. The carbon must have been stored in the deep ocean, and the transfer of carbon to the air and land during deglaciation must have affected the carbonate chemistry and carbon isotopic composition of the sea. <jats:bold> Yu <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="1084" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1193221">1084</jats:related-article> ) estimated how deep-water carbonate concentrations changed over the course of the last deglaciation and combined their results with <jats:sup>13</jats:sup> C/ <jats:sup>12</jats:sup> C data to show that carbon released by the deep ocean between 17.5 and 14.5 thousand years ago mostly stayed in the atmosphere as CO <jats:sub>2</jats:sub> , while between 14 and 10 thousand years ago, a substantial fraction was absorbed by the terrestrial biosphere. </jats:p>

<jats:title>Silicon Leakage</jats:title> <jats:p> Silicon is a major structural component of many marine organisms, whose chemistry is affected by oceanic nutrient distributions. To constrain nutrient changes since the last glacial period, <jats:bold> Ellwood <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="1088" related-article-type="in-this-issue" vol="330" xlink:href="10.1126/science.1194614">1088</jats:related-article> , published online 21 October) measured the isotopic compositions of silicon obtained from the skeletons of deep-sea sponges found in deep cores from the Atlantic and Pacific sectors of the Southern Ocean and compared them to the silicon signatures in the skeletons of modern sponges. The results indicate that nutrient redistribution, related to iron fertilization from dust deposition, boosted the growth of organisms that transferred silicon to mid-latitudes during the last glacial period. </jats:p>