Catálogo de publicaciones - revistas

<jats:title>Collisions give comets their shape</jats:title> <jats:p>The shape and structure of comets are relicts of collision processes from long ago. Despite recent and ongoing spacecraft missions that offer direct measurements of cometary nuclei, it is difficult to test what is important in comet shaping. Jutzi and Asphaug ran ∼100 three-dimensional collision simulations across a wide range of target and impactor masses and trajectories. Slow and less violent collisions produced the layering and bi-lobed shapes of actual comets.</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="6241" page="1355" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa4747">1355</jats:related-article> </jats:p>

<jats:title>Baboons follow the pack, not the leader</jats:title> <jats:p> How do groups of animals, including humans, make decisions that affect the entire group? Evidence collected from schooling animals suggests that the process is somewhat democratic, with nearest neighbors and the majority shaping overall collective behavior. In animals with hierarchical social structures such as primates or wolves, however, such democracy may be complicated by dominance. Strandburg-Peshkin <jats:italic>et al.</jats:italic> monitored all the individuals within a baboon troop continuously over the course of their daily activities. Even within this highly socially structured species, movement decisions emerged via a shared process. Thus, democracy may be an inherent trait of collective behavior. </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="6241" page="1358" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa5099">1358</jats:related-article> </jats:p>

<jats:title>How a receptor transmits a signal</jats:title> <jats:p> G protein–coupled receptors (GPCRs) transmit diverse external signals into the cell. When activated by an outside stimulus, they bind to a G protein inside the cell and accelerate exchange of a bound guanosine diphosphate (GDP) nucleotide for guanosine triphosphate, which initiates intercellular signaling. Dror <jats:italic>et al.</jats:italic> used atomic-level molecular dynamics simulations to show how GPCRs enhance GDP release. The G protein is dynamic and frequently adopts a conformation that exposes GDP even without the receptor bound. GPCR binding to this conformation favors an additional structural rearrangement that favors GDP release. The authors confirmed these predictions experimentally using double electron-electron resonance spectroscopy. </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="6241" page="1361" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa5264">1361</jats:related-article> </jats:p>

<jats:title>Designing proteins to self-assemble</jats:title> <jats:p> DNA has been used as a nano building material since the 1980s. Protein nanostructures have the potential to give greater geometric control and shape variability. Gonen <jats:italic>et al.</jats:italic> describe the computational design of proteins that self-assemble into two-dimensional arrays. These programmable protein lattices should enable new approaches in biomolecular structure determination and molecular sensing. </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="6241" page="1365" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa9897">1365</jats:related-article> </jats:p>

<jats:title>Bend me, shape me: Clathrin in action</jats:title> <jats:p> Endocytic clathrin-coated pits were among the first cellular structures described by electron microscopy over five decades ago. Despite this, the question remains: Does clathrin bind to the membrane as a flat lattice and then bend during coated pit invagination, or does clathrin assemble with a defined curvature as membranes invaginate? Avinoam <jats:italic>et al.</jats:italic> applied two state-of-the-art imaging approaches to resolve this conflict. They suggest that clathrin assembles into a defined flat lattice early in endocytosis, which predetermines the size of the vesicle. The assembled clathrin coat then rearranges through dynamic exchange of clathrin with the cytosolic pool to wrap around the forming vesicle. </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="6241" page="1369" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aaa9555">1369</jats:related-article> </jats:p>

<jats:title>Multifunctional pioneers</jats:title> <jats:p> Proteins surround cellular DNA to silence gene expression. Early in development, proteins such as pioneer transcription factors facilitate the opening of this silenced chromatin structure. Hsu <jats:italic>et al.</jats:italic> describe an additional role for the PHA-4 pioneer transcription factor in nematode worms. PHA-4 recruited RNA polymerase II to target promoters before transcriptional onset, and this activity preceded its chromatin-opening duty. The multifunctional role identified for PHA-4 may be shared by other pioneer factors. </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="6241" page="1372" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aab1223">1372</jats:related-article> </jats:p>

<jats:title>A degrading game plan for cancer therapy</jats:title> <jats:p> Certain classes of proteins that contribute to cancer development are challenging to target therapeutically. Winter <jats:italic>et al.</jats:italic> devised a chemical strategy that, in principle, permits the selective degradation of any protein of interest. The strategy involves chemically attaching a ligand known to bind the desired protein to another molecule that hijacks an enzyme whose function is to direct proteins to the cell's protein degradation machinery. In a proof-of-concept study, they demonstrated selective degradation of a transcriptional coactivator called bromodomain-containing protein 4 and delayed the progression of leukemia in mice. </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="6241" page="1376" related-article-type="in-this-issue" vol="348" xlink:href="10.1126/science.aab1433">1376</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>

<jats:p>Understanding stem/progenitor cells—which can develop into various types of tissue—are key to developing novel approaches for regenerative medicine. Techniques enabling the isolation of specific cell populations have advanced our ability to identify and characterize niche cell types which may be used to replace or engineer cells/tissue. The use of cell surface markers to isolate specific cell populations is one common method for separating cells; however, isolating live cells based on their RNA expression is a powerful new way enabling the study of small cell niches in nongenetically modified animal models and human tissue. In this webinar, we will hear from experts about different ways to isolate and characterize specific cell populations, including the nephrogenic progenitors that give rise to mature functional renal cells and mesenchymal stem cells which can differentiate into multiple cell types.</jats:p>

<jats:p>On this week's show: Using genetics to catch elephant poachers, the trouble with the letter R, and a roundup of daily news stories.</jats:p>