This Week in Science

Science  27 Aug 2010:
Vol. 329, Issue 5995, pp. 995
  1. Human Adenovirus Structures

    CREDIT: LAURIE JIANQIAN WANG, BASED ON RESULTS BY LIU ET AL., SCIENCE 329, 1038 (2010)

    Human adenoviruses may be a common cause of acute infections in humans, but they can also be used as vectors for vaccine and therapeutic gene transfer. Rational engineering of safe adenovirus vectors has been hampered by a lack of high-resolution structural information. Two papers now describe the structure of human adenovirus using complementary techniques. Reddy et al. (p. 1071; see the Perspective by Harrison) have determined the crystal structure at 3.5 angstrom resolution, while Liu et al. (p. 1038; see the Perspective by Harrison) solved the structure to 3.6 angstrom resolution by electron microscopy. Together the structures provide insights into viral assembly, stabilization, and cell entry mechanisms.

  2. Improving Earth Models

    The geophysical processes responsible for shaping the planet's surface and interior need largescale simulations, but to achieve high resolution at these scales is costly and tends to focus on gradual processes such as plate tectonics. By using large parallel supercomputers, Stadler et al. (p. 1033; see the Perspective by Becker; see the cover) have improved on a commonly used method—adaptive mesh refinement—to increase the resolution of global geodynamic models to the scale of a single kilometer and been able to reveal unexpected insights into localized processes, such as subduction zone mechanics, thermal anomalies in the lower mantle, and the speed of movement of oceanic plates.

  3. Swelling Pores

    Porosity is a key parameter when selecting materials for catalysts, chemical separations, gas storage, host-guest interactions, and related chemical processes. In most cases the porosity of a material is fixed. Rabone et al. (p. 1053; see the Perspective by Wright) have described a molecular material in which the size of the pores changed during the sorption process. The porosity increased because a dipeptide linker between metal centers reoriented during uptake of some gases, thus improving the capacity of the material to adsorb.

  4. Ant Variation

    Ants of the same genotype can exhibit numerous phenotypic forms and develop multiple functional castes within a colony. Bonasio et al. (p. 1068) sequenced the genomes of two ant species exhibiting differences in caste development—Camponotus floridanus and Harpegnathos saltator—and used the sequences to compare gene expression and identify differences in epigenetic gene regulation that lead to the phenotypic differences. Ants may offer a model system for studying the role of epigenetics in behavior and development.

  5. Environment Matters

    Stem cells isolated from muscle can be used for muscle regeneration, but only if the stem cells are fresh. Under standard cell culture conditions in the laboratory, muscle stem cells fail to proliferate efficiently and lose their regenerative capacity. Gilbert et al. (p. 1078, published online 15 July; see the Perspective by Bhatia) built an in vitro–culture system that resembles the physical characteristics in which muscle stem cells normally reside: a squishy elastic bed (rather than the hard slab of a plastic culture flask). Laminin tethered to hydrogels was used to generate substrates of varying elasticity. When cultured on these substrates, muscle stem cells remained undifferentiated and were able to support muscle regeneration when transplanted back into mice.

  6. Two Heads Are Better Than One

    When two people peer into the distance and try to figure out if a faint number is a three or an eight, classical signal detection theory states that the joint decision can only be as good as that of the person with higher visual acuity. Bahrami et al. (p. 1081; see the Perspective by Ernst) propose that a discussion not only of what each person perceives but also of the degree of confidence in those assignments can improve the overall sensitivity of the decision. Using a traditional contrast-detection task, they showed that, when the individuals did not differ too much in their powers of visual discrimination, collective decision-making significantly improved sensitivity. The model offered here formalizes debates held since the Enlightenment about whether collective thinking can outperform that of elite individuals.

  7. Forced Open

    CREDIT: LENHARDT ET AL.

    Traditionally, the study of reaction chemistry has relied on random encounters between molecules to initiate the proceedings. Heating and stirring increase the power and frequency of such encounters but provide little finer control. Very recently, chemists have learned how to initiate reactions more directly by embedding precursors in the backbone of a polymer large enough to manipulate with shear forces. Lenhardt et al. (p. 1057) applied this technique to a cyclopropyl ring-opening reaction. When the strained triangular carbon rings were embedded within a polymer, shear force applied by sonication ruptured their bonds as the polymer backbone stretched. The taut polymer then redirected the ring-opened intermediates toward a product differently arranged from that generated by simple heating.

  8. Black Holes as Tools

    When confronted with a difficult problem, physicists often resort to mapping it to a more tractable one. A good example of this strategy is provided by new developments linking string theory and condensed-matter physics to make theoretical connections between gravity and complex systems of interacting electrons. This theoretical convergence provides a description of Fermi liquids, which can be thought of as interacting systems of electrons whose excitations can be expressed in terms of non-interacting quasiparticles. Several interesting systems elude quasiparticle description, but Faulkner et al. (p. 1043, published online 5 August) have now developed a mathematical framework that describes the non-Fermi liquid represented by the strange metal phase of cuprate high-temperature superconductors. They calculate the electronic response and, for a particular value of a tunable parameter, recover the linear resistivity. Further development of this framework may allow elucidation of other exotic properties of the cuprates and similar complex systems.

  9. Cracking Up

    Transform faults perpendicular to mid-ocean ridges are some of the most prominently visual features on the sea floor. Because they form slowly over thousands of years, the lack of observational data means their mechanism of formation has remained controversial. Taking a numerical modeling approach, Gerya (p. 1047) suggests that due to asymmetric growth of the plate boundary, sections of the mid-ocean ridge become unstable and eventually rotate 90°. As the ridge continues to grow, the transform faults continue to develop long after their initiation. This mechanism also explains how offsets of these transform faults occur discontinuously as a result of new fractures at the ridge.

  10. Over the Moon

    Based on recent analyses of lunar rocks, it has been argued that the lunar interior contained much more water than previously thought. Sharp et al. (p. 1050, published online 5 August) measured the chlorine isotope content of lunar samples returned by the Apollo missions and found that the spread in their chlorine isotope composition is 25-fold greater than for rocks and minerals that have been measured from Earth and meteorites. This result implies that the hydrogen content of the Moon (and therefore its water content) is much lower than suggested by recent studies.

  11. Toward a General Flu Vaccination

    Current seasonal influenza virus vaccines are targeted against specific viral strains and do not provide broad, durable protection. Seasonal influenza vaccines induce protective antibody responses against regions of viral hemagglutinin (HA) that rapidly mutate so that very soon, the virus becomes resistant to vaccination. Conserved regions of HA also exist, and a major goal of influenza vaccine development is to design a vaccine that elicits antibodies against the conserved regions so that protection against a wide range of viral strains is achieved. Wei et al. (p. 1060, published online 15 July; see the Perspective by Doms) show that a combined HA DNA prime, followed by boosting with a seasonal vaccine, elicits broadly cross-reactive neutralizing antibody responses in mice, ferrets, and nonhuman primates, which were protective in mice and ferrets against heterologous influenza challenge. The neutralizing antibodies were directed against the conserved HA stem region, which indicates the possibility that a more broadly protective vaccine against influenza could be developed.

  12. Making Roots

    A tiny bunch of stem cells generates the bulk and diversity of plant roots. These cells are found at the root meristem and are themselves regulated by signaling inputs from a variety of sources. In Arabidopsis, Matsuzaki et al. (p. 1065) have identified a family of peptide factors that regulate these root stem cells. These peptides, known as root meristem growth factors, carry the post-translational modification, tyrosine sulfation, and are essential for maintaining the root stem cell niche.

  13. Plants' Modified SOS Call

    Plants have several ways of defending themselves against insect attack. The release of distinctive volatile chemicals betrays the location of herbivores to their predators, but volatile production can be slow and the pests may escape. Compounds known as green leaf volatiles are released immediately after damage, and Allmann and Baldwin (p. 1075) have found that, when attacked by tobacco hornworm (Manduca sexta) caterpillars, Nicotiana attenuata plants emit a compound that, when combined with an oral secretion from the caterpillar, is transformed into an attractant for the generalist hemipteran predator Geocoris pallidens, which preys on the hornworm eggs and young larvae. Thus, insect feeding activity can begin the process of plant defense before other protective volatiles are synthesized and emitted.

  14. Intracellular pH and Lipid Metabolism

    Intracellular pH regulates metabolism by poorly understood mechanisms, but biosensors are likely to be important in this process. Young et al. (p. 1085) took a systems-biology approach in yeast to identify in excess of 200 genes that regulate phospholipid metabolism. They found that the signaling lipid, phosphatidic acid, appeared to act as a cytosolic biosensor via the pH-dependent binding of protein effectors to phosphatidic acid. This pH-dependent mechanism directly affects gene expression and is involved in a pathway in which nutrient availability regulates phospholipid metabolism to control production of membranes.

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