Catálogo de publicaciones - revistas

<jats:title>Easy M</jats:title> <jats:p> Our immune systems can produce a vastly diverse repertoire of antibody molecules that each recognize and bind to a specific foreign antigen via a hypervariable region. However, there are a few bacterial antigens—such as Protein A, Protein G, and Protein L—that instead bind to the antibody's conserved regions and can bind to a large number of different antibodies. These high-affinity broad-spectrum antibody-binding properties have been widely exploited both in the laboratory and in industry for purifying, immobilizing, and detecting antibodies. <jats:bold> Grover <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6171" page="656" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1246135">656</jats:related-article> ) have now identified Protein M found on the surface of human mycoplasma, which displays even broader antibody-binding specificity. The crystal structure of Protein M revealed how Protein-M binding blocks the antibody's antigen binding site. This mechanism may be exploited by mycoplasma to escape the humoral immune response. </jats:p>

<jats:title>Stochasticity and Cell Fate</jats:title> <jats:p> Stochastic mechanisms can diversify cell fates in nervous systems. In the <jats:italic>Drosophila</jats:italic> retina, the stochastic distribution of color-sensing photoreceptors is controlled by the random, On/Off expression of the Spineless transcriptional regulator. <jats:bold>Johnston and Desplan</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6171" page="661" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1243039">661</jats:related-article> ) found that each allele of <jats:italic>spineless</jats:italic> makes an intrinsically random expression choice controlled by an enhancer and two silencer DNA elements acting at long range. <jats:italic>spineless</jats:italic> alleles communicate between chromosomes using activating and repressing mechanisms to determine the frequency of expression and coordinate expression state. These findings suggest critical roles for intrinsically random expression decisions and interchromosomal communication in stochastic cell fate specification. </jats:p>

<jats:title>From Channel to Sensor</jats:title> <jats:p> The coupling between voltage-activated calcium channels and calcium sensors of exocytosis on synaptic vesicles is a key factor that determines the timing and efficiency of transmitter release. It is still largely unclear how tight this coupling is at mature synapses in the central nervous system. <jats:bold>Vyleta and Jonas</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6171" page="665" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1244811">665</jats:related-article> ) found that mossy fiber boutons contain high concentrations of endogenous calcium buffers that normally limit the amount of calcium that reaches the calcium sensor responsible for neurotransmitter release. As a consequence, the calcium signal available to trigger release is small for the initial action potential. However, after high-frequency stimulation, the endogenous calcium buffer binds calcium and is less able to buffer calcium entry, which allows more calcium to reach the calcium sensor, increasing neurotransmitter release and synaptic facilitation. </jats:p>

<jats:title>Causing Chloride Changes</jats:title> <jats:p> Because intracellular chloride concentrations largely determine the direction and magnitude of current flow through GABA <jats:sub>A</jats:sub> channels, the stability of intracellular chloride concentration is important to maintain consistent synaptic inhibition. <jats:bold> Glykys <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6171" page="670" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1245423">670</jats:related-article> ) examined the mechanisms by which chloride gradients in neurons are established, using chloride imaging with transgenically expressed clomeleon dye. Surprisingly, intracellular chloride was not primarily determined by transporters. Instead, subcellular gradients of immobile anions generated inverse chloride gradients. </jats:p>

<jats:title>The Switch That Doesn't</jats:title> <jats:p> In mammals, a class of neurons in the brain normally switches from excitatory to inhibitory functions at birth. <jats:bold> Tyzio <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6171" page="675" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1247190">675</jats:related-article> ; see the Perspective by <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6171" page="620" related-article-type="in-this-issue" vol="343" xlink:href="10.1126/science.1250214"> <jats:bold>Zimmerman and Connors</jats:bold> </jats:related-article> ) studied how these neurons function in rat and mouse models of autism. The results show that oxytocin normally accelerates the switch in function, but in these two animal models, the switch fails. The dysfunction could be replicated in normal animals using an oxytocin receptor antagonist. </jats:p>

<jats:p>This week's show features a study on tracing autism's developmental roots and a roundup of stories from our daily news site.</jats:p>

<jats:p>A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.</jats:p>