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<jats:p>Certain human pathogens avoid elimination by our immune system by rapidly mutating the surface protein sites targeted by antibody responses, and consequently they tend to be problematic for vaccine development. The behavior described is prominent for a subset of viruses—the highly antigenically diverse viruses—which include HIV, influenza, and hepatitis C viruses. However, these viruses do harbor highly conserved exposed sites, usually associated with function, which can be targeted by broadly neutralizing antibodies. Until recently, not many such antibodies were known, but advances in the field have enabled increasing numbers to be identified. Molecular characterizations of the antibodies and, most importantly, of the sites of vulnerability that they recognize give hope for the discovery of new vaccines and drugs.</jats:p>

<jats:p>Problems can arise when vaccines and wild strains of a chicken herpesvirus recombine.</jats:p>

<jats:title>A Timely Structure</jats:title> <jats:p> The physiology and behavior of most organisms are inextricably aligned with the day/night cycle. In mammals, these daily rhythms are generated by a circadian clock encoded by transcriptional activators and repressors operating in a feedback loop that takes about 24 hours to complete. A key participant in this loop is a heterodimeric transcriptional activator consisting of the CLOCK and BMAL1 proteins. <jats:bold> Huang <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="189" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1222804">189</jats:related-article> , published online 31 May; see Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6091" page="165" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1224611">Crane</jats:related-article> </jats:bold> ) determined the crystal structure of a complex containing the PAS domains (implicated in protein-protein interactions) and the basic helix-loop-helix domains (implicated in DNA binding) from each protein. CLOCK and BMAL1 were observed to be tightly intertwined in an unusual asymmetric conformation, which may contribute to the stability and activity of the complex. </jats:p>

<jats:title>MMS19 Joins the CIA</jats:title> <jats:p> Iron-sulfur (Fe-S) proteins play a critical role in cell metabolism and particularly in DNA repair and replication. Mutants in eukaryotic gene <jats:italic>MMS19</jats:italic> are particularly sensitive to DNA damaging agents, suggesting that it is involved in DNA repair, but the mutations can also have other wide-ranging effects on the cell (see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6091" page="160" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225852">Gottschling</jats:related-article> </jats:bold> ). Now, <jats:bold> Stehling <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="195" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1219723">195</jats:related-article> , published online 7 June) and <jats:bold> Gari <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="243" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1219664">243</jats:related-article> , published online 7 June) show that in both yeast and humans, MMS19 functions as part of the cytosolic Fe-S protein assembly (CIA) machinery. The MMS19 is part of a specialized CIA targeting complex that plays a role late in cytosolic Fe-S protein assembly to direct Fe-S cluster transfer from the CIA scaffold complex to a subset of Fe-S proteins, including a number associated with DNA metabolism. </jats:p>

<jats:title>Influenza's Cryptic Constraint</jats:title> <jats:p> Because of the well-known pandemic potential of influenza viruses, it is important to understand the range of molecular interactions between the virus and its host. Despite years of intensive research on the virus, <jats:bold> Jagger <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="199" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1222213">199</jats:related-article> , published online 28 June; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6091" page="164" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1225539">Yewdell and Ince</jats:related-article> </jats:bold> ) have found that the influenza A virus has been hiding a gene in its small negative-sense RNA genome. An overlapping open reading frame was found contained in the PA viral RNA polymerase gene, which is accessed by ribosomal frameshifting to produce a fusion protein containing the N-terminal messenger RNA (mRNA) endonuclease domain of PA and an alternative C-terminal X domain. The resulting polypeptide, PA-X, selectively degrades host mRNAs and, in a mouse model of infection, modulated cellular immune responses, thus limiting viral pathogenesis. </jats:p>

<jats:title>Spin-Dependent Light Emission</jats:title> <jats:p> Spintronic devices exploit electronic currents that are spin polarized, which have an excess of one spin current over the other. One way to detect this polarization would be to create a light-emitting diode that is sensitive to spin polarization. Along these lines, <jats:bold> Nguyen <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="204" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1223444">204</jats:related-article> ) constructed a bipolar device in which an organic semiconductor was sandwiched between two ferromagnetic contacts whose relative polarization could be controlled by an applied magnetic field. Magneto-electroluminescence of the order of ∼1% was observed at a bias voltage of ∼3.5 V. The use of a deuterated organic polymer interlayer improved spin transport relative to polymers with hydrogen side groups, and a thin LiF buffer layer on the ferromagnetic cathode improved electron injection efficiency. </jats:p>

<jats:title>Moving Dislocations</jats:title> <jats:p> The mechanical properties of crystalline materials are limited by the presence and motion of defects caused by extra or missing atoms in the crystal lattice. Plastic deformation of a material causes these defects, known as dislocations, to move and multiply. Much is known about the motion of dislocations in three dimensions but less so in two. <jats:bold> Warner <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="209" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1217529">209</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="6091" page="161" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1224681">Bonilla and Carpio</jats:related-article> </jats:bold> ) used graphene as a model material to track dislocation dynamics in real time. The strain fields in the graphene sheet were mapped, which suggests that the dislocation motion is connected to the stretching, rotating, and breaking of individual carbon bonds. </jats:p>

<jats:title>Abiotic Martian Organics</jats:title> <jats:p> Understanding the sources and the formation mechanisms of organic carbon compounds on Mars has implications for our understanding of the martian carbon cycle. <jats:bold> Steele <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="212" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1220715">212</jats:related-article> , published online 24 May) present measurements of organic material in 11 martian meteorites, including the Tissint meteorite, which fell in the Moroccan desert in July 2011. Ten of the meteorites contain complex hydrocarbons encased within igneous minerals. The results imply that the organics formed as the magma melt crystallized and are thus of abiotic origin. </jats:p>

<jats:title>More Melting</jats:title> <jats:p> The last interglacial period, around 125,000 years ago, was 1° to 2°C warmer than the present, and the sea level was thought to be 4 to 6 meters higher. However, <jats:bold>Dutton and Lambeck</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="216" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1205749">216</jats:related-article> ), now suggest that sea level was possibly as much as 10 meters above current levels. Such a large excess of seawater would mean that the Greenland and Antarctic ice sheets melted much more than previously assumed, which has implications for how much sea-level rise we should expect with anthropogenic climate warming. </jats:p>

<jats:title>Acidification Blues</jats:title> <jats:p> The increase in the concentration of atmospheric carbon dioxide threatens the health of the ocean's ecosystems because of the resulting acidification of the ocean and the decrease in its carbonate saturation state. <jats:bold> Gruber <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="220" related-article-type="in-this-issue" vol="337" xlink:href="10.1126/science.1216773">220</jats:related-article> , published online 14 June) used a regional ocean model to project how the saturation state of aragonite, a form of calcium carbonate that is produced by many marine organisms, will change in the California Current System through the year 2050. The sea floor along many parts of the California coast is likely to become exposed to year-round aragonite undersaturation within the next 20 to 30 years, a situation that could severely reduce the range of habitats for marine shellfish. </jats:p>