This Week in Science

Science  28 Feb 2003:
Vol. 299, Issue 5611, pp. 1277
  1. I Really Hate to Get Wet

    The hydrophobicity of a material is mostly dependent on its surface chemistry, but can be altered by changing the surface topography. Superhydrophobic materials have been made, but usually only from expensive starting materials that required machining or etching to roughen the surface. Working with isotactic polypropylene, Erbil et al. (p. 1377) show that they can modify the standard gelation process to produce a rough polymeric coating on glass, aluminum, steel, and other polymers; this coating has a water contact angle around 160°.

    CREDIT: ERBIL ET AL.
  2. Basic Cluster Chemistry

    Despite the importance of the hydroxide (OH) ion in aqueous solution, a fundamental understanding of how it interacts with water has been thwarted by its very high affinity for protons, which creates structures such as [HO···H···OH]. Experimental studies of small clusters have also been plagued by thermally induced spectral broadening. Robertson et al. (p. 1367, see the Perspective by Huneycutt and Saykally) have obtained well-resolved vibrational spectra of water-solvated OH and, for comparison, F, that are surrounded by argon atoms. Absorption of vibrational energy is seen by the evaporation of weakly bound Ar atoms, a process that also keeps the main cluster cold. The primary hydration shells are relatively small and contain three water molecules for OH and four for F. In both cases, new features appear for larger clusters in the region typically associated with interwater hydrogen bonding.

  3. Probing Hydrated Protons

    Protons are extremely mobile in aqueous solution and are thought to move via exchange along hydrogen-bonded networks. Unfortunately, the vibrational spectrum of bulk water, which should provide structural insights into these networks, is broad and difficult to interpret in terms of specific cluster types. Asmis et al. (p. 1375, see the Perspective by Huneycutt and Saykally) now report vibrational spectra in the shared proton region of ion-trapped H+·(H2O)2 and D+·(D2O)2 in the range from 600 to 1900 wave numbers (cm−1). Radiation from a free electron laser allowed absorption to be detected by following the formation of H3O+ or D3O+ via multiphoton dissociation. The authors can assign hydrated proton bands and find that the stretching and bending modes of the O···H+···O moiety are highly anharmonic.

  4. Fishing for Fossils

    Some of the most diverse and well-preserved Yunnanozoans are found in China and provide a rare insight into metazoan evolution in the Cambrian. Shu et al. (p. 1380) describe a new species, Hiakouella jianshanensis, that has external gills and no evidence of a dorsal nerve chord. These specimens are the oldest and most primitive of the Yunnanozoans and are inferred to belong to the stem-group of deuterosomes.

  5. A Head of Its Time

    Java was established as an important locale for fossil hominids with the find of “Java Man,” a Homo erectus cranium, in 1891. These fossils have since played an important role in discussions of how and when H. erectus migrated across Asia and the extent to which later hominids interacted with them, because Java lies on the periphery of the Pleistocene Homo range. Baba et al. (p. 1384, see the news story by Gibbons) describe a new find of the top and back part of a Pleistocene H. erectus skull, including the cranial base. Their analysis provides information on how the form of the Homo head evolved with changes in brain capacity and supports the notion that the H. erectus population on Java became isolated from those elsewhere in Asia.

  6. Revisiting an Old Idea

    How does a limited repertoire of antibodies defend against diverse invading antigens? The idea that structurally different antibody conformations could bind to different antigens was first suggested by Pauling, but while there is kinetic evidence for such a conformational equilibrium, there has been no structural evidence. James et al. (p. 1362, see the Perspective by Foote) show by x-ray crystallography and kinetics that an antibody can exist in several conformations, each with its own binding specificity. While helping to cope with foreign antigens, conformational diversity run rampant might contribute to autoimmunity and allergy.

  7. Relative Comparisons

    From an analysis of humans and nonhuman primates, Boffelli et al.(p. 1391, see the Perspective by Gibbs and Nelson) show that closely related genomes provide more precise information on exons and regulatory regions than would be obtained from comparisons to distantly related genomes, such as that of the mouse. Comparisons among a small number of selected primates identified exon-intron boundaries in four regions and regulatory sequences for apolipoprotein A. Deletion of the putative regulatory regions affected promoter activity, indicating that they are likely to be functional.

  8. Spin Me Up, Scotty

    Millisecond pulsars are binary systems composed of a rapidly rotating, but old and weakly magnetized, neutron star that is in the process of being spun up by accretion of material from its companion. Stappers et al. (p. 1372) obtained Chandra X-ray Observatory images of x-ray structures in B1957+20. These structures show that the pulsar winds are relativistic and that the neutron star loses rotational energy through these relativistic particles, just like young pulsars. Thus, old and young pulsars have similar avenues for rotational energy loss, and refined models are needed to understand why their spin rates and magnetic field strengths differ so.

    CREDIT: STAPPERS ET AL.
  9. Protein Inspectors

    Quality control in the endoplasmic reticulum (ER) is the process by which the proper folding and assembly of newly synthesized secretory and membrane proteins are assessed such that only correctly folded proteins are approved for further transport along the secretory pathway. In two papers, Oda et al. and Molinari et al. (p. 1394 and p. 1397, see the Perspective by Sifers) elucidate the roles of a protein termed EDEM and an ER membrane-associated molecular chaperone, calnexin. Together, they act to recognize the folding status of glycoproteins and, when appropriate, pass them along to the ER degradation machinery.

  10. Flexibility Favors Diversity

    Although recent research has identified complex interactions among many species in large food webs, ecological theory predicts that these food webs are unstable and cannot persist. Kondoh (p. 1388) resolves this paradox by incorporating adaptative evolution into food-web models. Foraging adaptation provides a food web with “flexibility,” which creates a strong positive relationship between food-web complexity and community stability. The model suggests how biodiversity is maintained in complex food webs and points to the central roles of genetic diversity, local adaptation, and a community's evolutionary history in maintaining local biodiversity.

    CREDIT: KONDOH
  11. Pumping Protons to Grow

    In the immune system, mature dendritic cells are specialists at capturing antigens that they then present to T cells. Trombetta et al. (p. 1400) compared the characteristics of immature and mature dendritic cells and discovered that part of the maturation process involved the assembly of additional proton pumps in the lysosomal membrane of the dendritic cells. This leads to a lower pH within endocytic compartments and more efficient processing and presentation of antigens.

  12. How to Stay Flat

    Although development is the sum of its parts, the theoretical principles that enforce its coherence have been hard to observe. Nath et al. (p. 1404, see the Perspective by McConnell and Barton) analyze the growth of the snapdragon leaf and find that the shape of the leaf is determined by the shape of a wave of differentiation that passes from the tip to the base of the leaf. Molecular analysis of a mutation in the gene CINCINNATA, which results in crinkly leaves, combined with theory to generate insights into how cell cycle arrest in individual cells can be coordinated to generate the desired leaf shape.

  13. Less Steroid Leads to Longer Life

    Ecdysone is a steroid hormone best known for triggering the transition from larvae to adult in many insects. The biosynthetic machinery for ecdysone operates in the adult, too, but its purpose has been unclear. Simon et al. (p. 1407) show that deficiencies in the ecdysone signaling system of adult Drosophila—either in biosynthesis or in its receptor—lead to flies with extended life-spans and an increased resistance to stress, without concomitant decreases in fertility or activity. Thus, steroids may be important players in the endocrine network that affects life-span in flies and other organisms.

  14. Inhibiting a Pump Within a Pump

    Heart failure affects nearly 5 million people in the United States. Most inherited forms of heart failure have been linked to defects in cardiac contractile proteins. Schmitt et al. (p. 1410) show that heart failure can be initiated by disturbances of calcium metabolism in heart muscle cells. Humans with an inherited form of congestive heart failure were found to have a mutation in phospholamban (PLN), a protein that inhibits the cardiac sarcoplasmic reticulum Ca2+-ATPase (SERCA2a). Subsequent experiments revealed that the mutant PLN causes constitutive inhibition of SERCA2a, leading to alterations in Ca2+ kinetics.

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