Editors' Choice

Science  17 Sep 2010:
Vol. 329, Issue 5998, pp. 1442
  1. Physiology

    Protecting Against Cold

    1. Caroline Ash

    Even during the Antarctic winter, parasitic ticks of birds remain active. These arthropods spend much of their lives clinging to vegetation and waiting for warm-blooded prey to pass within reach. Neelakanta et al. wondered whether ticks possess any special capacity for surviving the environmental extremes to which they are inevitably exposed. The black-legged tick Ixodes scapularis serves as a vector for the bacterium Anaplasma phagocytophilum, which causes disease in humans as well as in a range of wild mammals. Heavy loads of bacteria in the ticks correlated with good winter survival and high activity of the arthropods. It appears that the bacterium stimulates the production of antifreeze glycoproteins in its host, suggesting a mutualistic arrangement. Antifreeze proteins coat the surfaces of nucleated ice crystals and reduce the rate at which they grow. These findings are consistent with the idea that some human pathogens may have originated via opportunistic invasions from microorganisms that were originally invertebrate symbionts.

    J. Clin. Invest. 120, 3179 (2010).

  2. Chemistry

    Fueling Renewable Feedstocks

    1. Jake Yeston

    As petroleum supplies dwindle and concerns mount about the adverse environmental impact of chemical waste streams, chemists are increasingly on the lookout for better ways to derive the feedstocks used to manufacture plastics, medicines, and numerous other carbon-based societal necessities. One promising route to partially oxidized intermediates such as acetate is the fuel cell–mediated reaction of alcohols with oxygen. Direct alcohol fuel cells can produce electricity while halting oxidation at substances more functionally diverse and useful than CO2. Most such fuel cells rely on either heterogeneous precious metal catalysts or oxidative enzymes. Annen et al. present a fuel cell design that uses well-defined molecular rhodium complexes, supported on a conductive surface, to catalyze ethanol oxidation to acetate. The short-term power density of a prototype cell approached that of the heterogeneous systems, greatly exceeding the typical performance of enzymatic devices, while at the same time offering the tunability and depth of mechanistic insight associated with molecular catalysts. Analysis of the cell after approximately 2 days of running time confirmed that the rhodium complex remained largely intact, although tight coordination of the acetate product reduced its activity.

    Angew. Chem. Int. Ed. 49, 10.1002/anie.201002234 (2010).

  3. Chemistry

    Manganese Sightings

    1. Phil Szuromi

    The biological role of manganese is not limited to its presence in enzymes. In cells, Mn2+ ions that are weakly bound to water, phosphates, carboxylates, or other ligands may combat oxidative stress by reacting with species such as superoxide—or, if present in sufficient concentration, they can also be toxic. The nature of Mn2+ ligand speciation may underlie the varying abilities of different cell types to resist oxidative stress, but the rapid interchange of ligands necessitates in situ methods to study their effect in cells. McNaughton et al. have now shown that a magnetic resonance technique, proton and phosphorus-31 pulsed electron-nuclear double resonance, can be used to assess intracellular phosphate coordination to the paramagnetic manganese ions. The study revealed that the oxidative-stress resistance of mutants of Baker's yeast (Saccharomyces cerevisiae) correlated with the concentration of orthophosphate complexes, which in vitro studies have shown to exhibit superoxide dismutase activity. Having determined average speciation across the entire cell, the authors next plan to probe variations in intact isolated organelles.

    Proc. Natl. Acad. Sci. U.S.A. 107, 15335 (2010).

  4. Immunology

    Recycling Overdrive

    1. Kristen L. Mueller
    CREDIT: SEIFERT ET AL., CELL 142, 613 (2010)

    The degradation of polyubiquitylated proteins by the proteasome is critical for maintaining homeostasis in eukaryotic cells. Ubiquitin is a tag that is attached to proteins that are damaged or need to be destroyed. Proteasomes in cells of the immune system incorporate alternative catalytic subunits, and these immunoproteasomes can also be found in non-immune cells in response to inflammation. Immunoproteasomes exhibit altered enzymatic activity that results in the production of peptides that are particularly well suited for binding to the proteins that present antigenic fragments to cytotoxic T cells. Mice that are deficient in these alternative subunits, however, exhibit only modest changes in antigen presentation, and so the function of immunoproteasomes has remained a mystery. One of the outcomes of inflammation is oxidative stress, which results in the formation of nascent oxidantdamaged proteins. Seifert et al. report that mouse cells up-regulate the ubiquitylation machinery in response to inflammation, targeting oxidant-damaged proteins for degradation by the immunoproteasome. In the absence of immunoproteasomes, harmful aggregates of damaged proteins (green) accumulate—for instance, in the liver. These results suggest that rather than antigen presentation, immunoproteasomes are critical for protecting cells against oxidative damage during bouts of inflammation.

    Cell 142, 613 (2010).

  5. Climate Science

    How Long is the Pacific's Reach?

    1. H. Jesse Smith

    Kim et al. recently suggested that the influence of sea surface warming events in the Central Pacific Ocean has contributed to more frequent landfall of North Atlantic tropical cyclones in the Gulf of Mexico and Central America (Reports, 3 July 2009, p. 77). If that were true, the predictability of Atlantic hurricane behavior could be improved by taking into account the state of the Pacific. Lee et al. have now performed an independent analysis of Central Pacific warming (CPW) events since 1969 and conclude that the relation between the two phenomena is not as strong as claimed. In fact, they suggest that the size of the Atlantic Warm Pool can explain the frequency of landfall, without invoking a remote influence from the tropical Pacific at all. They thus argue that it is premature to associate CPW events with that aspect of cyclone activity in the Gulf of Mexico and Caribbean Sea. They maintain that longer time series and more data, as well as corrections for the state of North Atlantic sea surface temperature patterns, are needed in order to identify a possible remote influence of the CPW on Atlantic hurricane landfall.

    Geophys. Res. Lett. 37, L17702 (2010).

  6. Economics

    Weather Forecast

    1. Brad Wible

    To manage the risk of your company's gas pipeline business hemorrhaging money during a warm winter, or of your string of beachfront condominiums lying empty during an especially intense hurricane season, you could enter the weather derivatives market. Traders bet on weather, with payments made when temperatures, precipitation, and other meteorological indices reach target levels. This market originated in the U.S. energy sector in the mid-1990s and was valued at $32 billion in 2007–2008. Randalls explores how the U.S. and UK me teorology systems influence, and are influenced by, the market. The U.S. system features a core of basic public data and services, allowing a larger private sector to flourish, whereas the UK government system exerts more control over data and services, charging for access. The demands of the market vary. Some contracts require highly accurate data, where a single degree can affect profits dramatically, whereas other contracts depend on marketwide consistency (that is, having the same averages and standard deviations as the rest of the market). Public meteorologists' attempts to market new products, such as probabilistic forecasts, which may promise greater scientific understanding, confront resistance from traders who may prefer simpler, yet more business-ready deterministic models. With increasing pressure to justify government investment, meteorology must strike a fine balance between the pursuit of science in the public interest and provision of services of commercial value.

    Soc. Stud. Sci. 40, 10.1177/0306312710378448 (2010).

  7. Behavior

    Intrinsic Ability

    1. Gilbert Chin

    Controlled variation is the essence of experimentation, but naturally occurring variation can be an equally powerful source of evidence, especially in situations where humans are the objects of study. Establishing the link between brain and behavior, and hence identifying potentially causal pathways, has become more feasible with improvements in neuroimaging technology. Forstmann et al. demonstrate how this approach can be applied (for another instance, see Fleming et al., Science, Reports, p. 1541) by comparing the trade-off between speed and accuracy in a simple perceptual task to the size of the white-matter tracts from the cortex to the striatum and to the subthalamic nucleus, which they localized using high-resolution 7T structural MRI. People were shown a cloud of dots in which some were moving steadily to the left or the right and the rest were moving randomly. On separate trials, they were cued to emphasize either speed or accuracy in identifying the direction. The individual differences in the flexibility with which they were able to adjust their response thresholds—that is, how much information they accumulated before making a choice—correlated positively with the structural connectivity of the cortex and the striatum and not with the cortico–subthalamic nucleus tract.

    Proc. Natl. Acad. Sci. U.S.A. 107, 10.1073/pnas.1004932107 (2010).