This Week in Science

Science  14 Aug 2009:
Vol. 325, Issue 5942, pp. 791
  1. MOFs with Guest Rooms

    CREDIT: QIAOWEI LI

    Metal organic framework (MOF) solids typically boast large pores in their crystal lattices that can accommodate molecular guests and are useful as compact media for gas storage. However, guest binding has generally relied upon nonspecific interactions with the framework components. Li et al. (p. 855) have now prepared MOFs that incorporate macrocyclic ethers into the structural ligands comprising the framework walls within which certain cationic guests can bind quantitatively and site-specifically, akin to the molecular docking of drug molecules within protein receptors.

  2. Friendly Fire

    Hints of the use of more advanced materials by humans, including symbolic marking and jewelry, appear about 75,000 years ago or so in Africa. Brown et al. (p. 859; see the Perspective by Webb and Domanski) now show that these early modern humans were also experimenting with the use of fire for improved processing of materials. Replication experiments and analysis of artifacts suggest that humans in South Africa at this time, and perhaps earlier, systematically heated stone materials, including silcrete to improve its flaking properties in making tools.

  3. Gamma-Ray Pulsar Bonanza

    Most of the pulsars we know about were detected through their radio emission; a few are known to pulse gamma rays but were first detected at other wavelengths (see the Perspective by Halpern). Using the Fermi Gamma-Ray Space Telescope, Abdo et al. (p. 840, published online 2 July; see the cover) report the detection of 16 previously unknown pulsars based on their gamma-ray emission alone. Thirteen of these coincide with previously unidentified gamma-ray sources, solving the 30-year-old mystery of their identities. Pulsars are fast-rotating neutron stars. With time they slow down and cease to radiate; however, if they are in a binary system, they can have their spin rates increased by mass transfer from their companion stars, starting a new life as millisecond pulsars. In another study, Abdo et al. (p. 845) report the detection of gamma-ray emission from the globular cluster 47 Tucanae, which is coming from an ensemble of millisecond pulsars in the cluster's core. The data imply that there are up to 60 millisecond pulsars in 47 Tucanae, twice as many as predicted by radio observations. In a further companion study, Abdo et al. (p. 848, published online 2 July) searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars outside of stellar clusters, finding gamma-ray pulsations for eight of them. Their properties resemble those of other gamma-ray pulsars, suggesting that they share the same basic emission mechanism. Indeed, both sets of pulsars favor emission models in which the gamma rays are produced in the outer magnetosphere of the neutron star.

  4. Porous Anodes for Solid Oxide Fuel Cells

    CREDIT: SUZUKI ET AL.

    Fuel cells that use ion-conducting oxides as the electrolyte can be highly efficient and use hydrocarbon fuels directly. However, their very high operating temperatures (usually above 700°C) can lead to unwanted reactions with their electrode materials and premature degradation of their performance. In order to improve fuel-cell electrochemical performance, Suzuki et al. (p. 852) describe a route for increasing the porosity of the anode material, which contains nickel oxide and zirconia doped with scandium and cerium and is fabricated as a cylinder. Subsequent coating and firing steps added a layer of a zirconia-based electrolyte and the (La,Sr)(Co,Fe)O3 cathode. The resulting fuel-cell power density exceeded 1 watt per square centimeter at 600°C, and its performance improved as hydrogen fuel velocities were increased through the cell.

  5. Lysine Acetylation Catalog

    Covalent posttranslational modification is an essential cellular regulatory mechanism by which the activity of proteins can be controlled. Advances in mass spectrometry made it possible for Choudhary et al. (p. 834, published online 16 July) to assess the prevalence of lysine acetylation throughout the whole proteome. Acetylation is much more widespread than previously appreciated and occurs on proteins participating in all sorts of biological functions. Acetylation can influence susceptibility of proteins to phosphorylation and occurs frequently on enzymes that control the modification of other proteins by covalent ubiquitination and on proteins that form large macromolecular complexes. The findings also help to characterize the actions of lysine deacetylase inhibitors, which have shown clinical promise in treatments for cancer.

  6. Strategic Reading

    Scanning the scientific literature these days is more akin to flicking through TV channels and trying to watch everything at once. Often the outcome of the scan will not have located any specific paper and it is unlikely to have involved any in-depth reading, but it achieves an undefined “assimilation” of knowledge from a melange of titles and abstracts, tables, indexes, databases, and figures. Renear and Palmer (p. 828) review how scientists use new forms of the “literature” and how the ascendance of novel computing technologies will combine to revolutionize the way scientific data is accessed, synthesized, and turned to practical use.

  7. Why Birds of a Feather Flock Together

    The biological determination of sociality, that is, why one might choose to associate with others and how many, has been unclear. Goodson et al. (p. 862) show that in gregarious finches, oxytocin-like receptors and their cognate ligand, mesotocin, are associated with group size choices. Receptor distributions clearly differentiate territorial species from flocking species. Furthermore, these compounds appear to play a role in affecting choice in affiliation in mammals, and thus may be conserved across evolutionary distant taxa.

  8. Reducing Sleep Length

    Humans, like most animals, need their beauty sleep. But the preferred amount and quality of sleep varies between individuals—and some individuals exhibit a heritable, lifetime tendency to sleep less then 6 hours per night. He et al. (p. 866; see the Perspective by Hor and Tafti) identified a mutation in humans associated with people who regularly require shorter than usual sleep duration. The mutation is found in the gene encoding a transcriptional repressor, DEC2, already implicated in regulation of circadian rhythms. Related mutations introduced into mice and flies similarly resulted in shortened sleep phases.

  9. Friction in Microscopic Motor

    Friction arises because adhesive bonds between two bodies must be broken in order for them to move relative to each other. Now Bormuth et al. (p. 870; see the Perspective by Veigel and Schmidt) have used single molecule measurements to characterize the frictional drag force of kinesin-8 motor proteins interacting with their microtubule track. Friction, arising from rupture of bonds with the track, constrains the speed and efficiency of the motor protein.

  10. Monkey See Human Do

    CREDIT: ANNA SCHMIDT

    Imitation has been put forth as one mechanism through which cultural learning occurs. Paukner et al. (p. 880; see the Perspective by Call and Carpenter) now demonstrate that imitation may also contribute to prosocial behaviors. Capuchin monkeys behaved in a more affiliative manner—as assessed by direction of gaze, physical proximity, and token exchange—toward humans who imitated them as compared to humans who performed the same movements, but did not do so simultaneously.

  11. Ironing Out Stress

    The peptide hormone, hepcidin, is secreted from the liver in response to extracellular factors, including inflammation, and regulates iron homeostasis by controlling transmembrane iron transport. Vecchi et al. (p. 877) showed that intracellular stress signals in the endoplasmic reticulum also control hepcidin expression and can thus modulate local or systemic iron traffic. This mechanism occurs through the transcription factor CREBH, which is a known mediator of the inflammatory response. Collectively, the results suggest a direct link between the intracellular stress response, innate immunity, and iron metabolism.

  12. Diverting Asperger Deficit

    Placement of Asperger syndrome within the family of autism spectrum disorders (ASD) has always been a bit uneasy; although people with Asperger syndrome do exhibit the core impairments in social interaction and communication that are characteristic of ASD, they nevertheless perform well on tests that are thought to assess the ability to mentalize or to possess Theory of Mind skills. One of the classic tests of mentalizing ability is the false-belief task, in which subjects must be able to represent their own beliefs (true) and another's beliefs, which are false because they have not been given complete information, such as not having seen the transfer of a piece of candy from one drawer to another. People with Asperger syndrome succeed at the verbal form of the false-belief task, yet Senju et al. (p. 883, published online 16 July) show that this is owing entirely to their having learned how to cope with an existing and still demonstrable deficit in an implicit version of the false-belief task. That is, the core impairment is present, but conscious and explicit learning allows them to compensate.

  13. Dynamin-Related Proteins' Little Helper

    Dynamin-related proteins (DRPs) comprise a family of large guanosine triphosphatases that self-assemble to form different nucleotide-dependent structures that associate with and change the behavior of intracellular membranes. Many studies have focused on how dynamins function by themselves as machines. In cells, however, DRPs cannot function alone and require additional, associated proteins (DAPs) to perform their functions. The exact mechanistic roles that DAPs play are not known. Lackner et al. (p. 874) address this question using the mitochondrial division machine that requires the DRP, Dnm1. The Dnm1-associated protein, Mdv1, functions as a conformational and structural nucleator for Dnm1 self-assembly.

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