This Week in Science

Science  05 Apr 1996:
Vol. 272, Issue 5258, pp. 9
  1. Infant diarrhea and rotavirus vaccines

    Rotavirus infection causes almost 1 million infant deaths annually in developing countries through acute diarrhea. Although oral vaccines against rotavirus infection have been developed, some are not effective in all populations (modified live oral vaccines) or provide immunity only against the four major rotavirus serotypes (see the Perspective by Glass et al., p. 46). Identification of viral gene products associated with virulence may lead to new vaccination strategies. Ball et al. (p. 101) show that a nonstructural rotavirus protein, NSP4, acts as an enterotoxin and induces diarrhea in young mice. Burns et al. (p. 104) studied the protective effect of antibodies that were secreted in mice from “backpack” tumors. Two immunoglobulin A antibodies to an inner viral capsid protein, VP6, were effective in preventing and resolving rotavirus infections, but antibodies to an outer viral capsid protein, VP4, were not effective.

  2. Earliest origins

    The Anthropoidea (the primate suborder that includes monkeys, apes, and humans) seems to have originated about 45 to 50 million years ago, although the early ancestor and whether the origin was in Africa or Asia has been debated. One concern was whether recently discovered isolated teeth from China truly represented an early anthropoid. Beard et al. (p. 82) now describe a complete lower jaw from a new genus of anthropoids in Eocene rocks of Shaxi Province, China. This fossil shows both primitive and derived characteristics that are unlike those of other primates.

  3. Really fine print

    Nanotechnology requires the routine fabrication of smaller and smaller units. For a technique to become useful in the manufacturing of commercially viable nanodevices, it has to prove low cost, high throughput and reproducibility. Chou et al. (p. 85) present a technique, based on compression molding of thermoplastic polymers, that allows the manufacture of well-defined 25-nanometer features. The technique does not require a sophisticated apparatus, and allows high throughput by imprinting a large area at once.

  4. C60 catalyst

    The soccer-ball pattern of carbon atoms in C60 satisfies the isolated pentagon rule (IPR), and other possible isomers would be thermodynamically unstable by comparison. Higher energy forms could rearrange their carbon bonds and satisfy the IPR, but these pathways often increase strain and have high energetic barriers. Eggen et al. (p. 87; see the Perspective by Mintmire, p. 45) explain how attaching a carbon atom to the fullerene can lower the barriers to rearrangement substantially

  5. Throwing a wrench

    Moving one's arm as, for instance, in throwing a baseball, requires no conscious computation of trajectory and velocity. Is this because the brain is an effortless computer of movement or because the intrinsic mechanical properties of the arm are used to reduce the problem to a series of muscle equilibrium points? Gomi and Kawato (p. 117; see the news story by Pennisi, p. 32) describe a machine used to measure arm stiffness during multijoint movement. They find that the arm velocities produced by humans do not correspond to those calculatedassuming that the equilibrium points are targeted sequentially and thus conclude that more complex motor commands are necessary.

  6. Homogenized NMR

    Higher magnetic fields can lead to sharper nuclear magnetic resonance (NMR) spectra. However, the field must be made homogeneous to about one part per billion, which is often done with additional fields from shimming coils. Very high field magnets are usually impractical for high-resolution NMR work. Vathyam et al. (p. 92) have devised a detection sequence that removes inhomogenity by referencing the spectrum of a solute molecule to nearby solvent molecules through zero-quantum coherences. Possible applications include NMR structures of proteins.

  7. No special hydrogen bonds

    Recently, it has been proposed that hydrogen bonds can contribute in a special way in enzymatic catalysis: a strong low-barrier H bond can form that stabilizes the transition state by matching the acidities (pKa's) of the H bond donor and acceptor. Shan et al. (p. 97) tested this hypothesis by studying the equilibria of a series of substituted phthalate monoanions in nonaqueous solvents. The free energy of formation of the H bonds did not vary even when the pKa's of the donor and acceptor were matched.

  8. Shrinking ceramics

    When minerals or ceramics are heated up, they usually expand. Mary et al. (p. 90) report on a material that shrinks when heated over a 1000-kelvin temperature interval and even through a solid-solid phase transition. The shrinking is attributed to coupled rotations of lattice units, leading to anisotropic thermal vibrations. This property could be used for devising materials with zero thermal expansion, either as composites or by tuning the lattice composition (see the news story by Service, p. 30).

  9. Stranded mutations

    Mutations of DNA in the wild provide the groundwork for evolution. Because DNA is replicated in a continuous manner on the leading strand, and discontinuously on the lagging strand by the synthesis and joining of Okazaki fragments, it has been suggested that mutations might more easily accumulate in the lagging strand. Francino et al. (p. 107) have examined the prevalence of mutations on the leading and lagging strands of multiple genes in natural strains of Escherichia coli and Salmonella. They find no difference in mutation rates on the leading and lagging strands; instead they find that the coding strand had more C to T substitutions than the noncoding strand. These differences may imply that transcription-coupled repair took care of DNA damage on the transcribed (noncoding) strand.

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