This Week in Science

Science  20 Mar 2009:
Vol. 323, Issue 5921, pp. 1535
  1. Hello to Hurdia


    Anomalocaridids are among the most famous of all Cambrian organisms, and have been dubbed the “T. rex of the Cambrian” because of their large size and inferred predatory habits. Hurdia, described by Daley et al. (p. 1597), is the most common anomalocaridid in the Burgess Shale fossil beds in Canada. Hurdia has recently attracted interest because of its significance in arthropod evolution, yet it has remained effectively unknown because its fossil remains were misattributed among several other genera. Hurdia, with its unique and remarkable frontal carapace, provides critical new data on the gill structure of stem-group arthropods with a direct bearing on the recent debate about arthropod limb evolution.

  2. Making Muscles Out of Materials

    New materials are being investigated that can convert electrical, chemical, thermal, or photonic energy into mechanical energy. Aliev et al. p. 1575; see the Perspective by Madden) described the mechanical properties and electrostatic actuation of very low density multiwalled carbon nanotube sheets formed into aerogels. By electrostatically charging the sheets, a large expansion occurred in the direction perpendicular to the nanotube orientation, and a smaller contraction occurred parallel to the stretch direction. This work points the way to developing novel materials with highly directional mechanical properties.

  3. Two-in-One Antibody


    Textbook definitions of antibodies emphasize the exquisite specificity with which these proteins bind their target antigens. New research suggests that this “one antibody-one antigen” paradigm can be tweaked in the laboratory. Working with an engineered library of variants of Herceptin, a therapeutic monoclonal antibody targeting the breast cancer growth factor HER2, Bostrom et al. (p. 1610; see Perspective by Parren and Burton) successfully selected variants which had antibody-combining sites that simultaneously bound with high affinity to a second cancer-relevant antigen, vascular endothelial growth factor (VEGF). In preliminary assays of efficacy, the two-in-one antibodies inhibited HER2- and VEGF-mediated cell proliferation in vitro, as well as tumor growth in mice, thus indicating the feasibility of a single therapeutic for cancer treatment.

  4. Ordered into Superconducting

    In unconventional superconductors, such as the cuprates, electrons form Cooper pairs by mechanisms other than electron-phonon coupling. These systems have a high density of defects and are chemically doped, so it can be difficult to observe smooth transitions between the superconductor and the parent electronic state from which they form. Takabayashi et al. (p. 1585; see the Perspective by Tosatti) showed that a particular phase of the alkali fulleride superconductor Cs3C60, which is well-ordered and exhibits a body-centered cubic symmetry, transformed from a spin-1/2 antiferromagnetic insulator to a superconductor as pressure was applied. The transition was purely electronic, in that no structural changes or disordering occurred. The dependence of the transition temperature on pressure was not accounted for by the standard model for superconductivity.

  5. Improving Parkinson's Treatment

    Deep brain stimulation has become a popular procedure for the treatment of motor symptoms in Parkinson's disease. However, it is an invasive surgical technique and people have been trying to find alternative methods that carry less risk. Fuentes et al. (p. 1578; see the cover; see the news story by Miller) tested electrical stimulation of the spinal cord dorsal column as an alternative strategy in animal models of Parkinson's disease. They found that corticostriatal activity patterns preceded voluntary motor actions, which may offer some explanation for the mechanisms underlying volitional movements. Dorsal column stimulation markedly improved motor functions, and enhanced pharmacological treatment in the animals, and looks as if it holds considerable promise for the treatment of Parkinson's disease patients.

  6. Heating the Solar Atmosphere

    The temperature of the Sun increases markedly as one moves from its surface to the outer layers of its atmosphere. Types of plasma waves called Alfvén waves, that are hypothesized to be incompressible and driven by magnetic tension, are considered to be the best explanation for how energy is transported through the solar atmosphere, but their unambiguous detection is still in doubt. Jess et al. (p. 1582; see the news story by Kerr) obtained high-resolution images of the Sun and found oscillations that bear the signatures of torsional Alfvén waves and that carry sufficient energy to heat the solar atmosphere.

  7. Meta Addition

    Friedel-Crafts reactions are among the oldest adopted in modern organic chemistry and have been used for over a century to attach various atoms around benzene rings and create components of dyes, drugs, and a wide range of functional materials. These reactions install incoming groups on the ring carbons adjacent to or diametrically opposite electron-donating substituents such as amines. Modifying the intermediate (or meta) sites, two carbons away from existing substituents, has been challenging. Phipps and Gaunt (p. 1593; see the Perspective by Maleczka) discovered a copper catalyst that selectively adds incoming phenyl groups to the meta positions of amide-substituted benzenes. This kind of catalysis opens the way to the development of novel agrochemicals and pharmaceuticals.

  8. Methylation Rescue

    Methylation of genomic DNA occurs with high frequency at transposons and repetitive DNA sequences to repress transcription of these potentially damaging genome features. Methylation patterns are normally inherited during cell division as the methylated parental DNA strand provides a template for the methylation of the daughter strand. But sometimes methylation marks are ablated and lost in all subsequent generations. Teixeira et al. (p. 1600, published online 29 January; see the Perspective by Law and Jacobsen) found that Arabidopsis recovered methylation marks in a process requiring meiosis and the RNA interference-dependent DNA methylation machinery. After one to three generations, original methylation levels were recovered. This mechanism not only helps to maintain genome stability, but might also permit adaptive responses in epigenetic inheritance.

  9. Conducting 3D Printing


    One challenge to the development of more robust, flexible, or stretchable electronics is the printing of electrodes within devices and between devices. Ahn et al. (p. 1590, published online 12 February; see the Perspective by Gates) have formulated concentrated silver nanoparticle inks that can be printed in three dimensions. The electrodes are self-supporting and can be patterned in complex ways as planar or 3D forms on a wide variety of substrates. Once sintered at moderate temperatures, the colloidal particles fuse together to make wires with electrical resistivities that approach the value for bulk silver.

  10. Sorting Light Receptors

    In the retina, cyclic nucleotide gated (CNG) channels initiate the electrical response to light in the sensory cilia of the rods. The channels are exclusively localized to outer segments of the cilia, but how they are positioned has been largely unknown. Working on Xenopus, Kizhatil et al. (p. 1614) showed that the CNG-β subunit bound to ankyrin-G, a membrane scaffolding protein, is not only required for the post-Golgi transport of CNG channels, but is also required for rod outer segment development. A human mutation in the CNG-β subunit disrupts this targeting mechanism and is associated with retinitis pigmentosa. Similar ankyrin-G-based mechanisms may occur in olfactory cilia, in the sperm flagella, and other sites.

  11. Take My Word for It

    On issues of fact, such as whether the bus has just passed, we usually feel comfortable to accept information from a stranger; in situations where emotions are involved we are more likely to rely on our own feelings than what others report. Gilbert et al. (p. 1617) demonstrated that this confidence may be misplaced. In a speed-dating scenario, women were asked for their subjective evaluations before and after a 5-minute encounter with a single man. The women who had only been supplied with a man's profile and photograph fared significantly worse in predicting their after-the-fact reaction to their date than women who were supplied with an evaluation of a man from their predecessor.

  12. Mother Knows Best

    Gouldian finches have two color morphs that tend to mate true. Pryke and Griffith (p. 1605) showed that females forced to mate with males of the opposite morph have more sons and invest less effort in rearing them than if allowed to mate with their own type. But if the males are painted to resemble the females' preferred mates, the duped females will readjust their behavior and the sex ratio of the eggs. The results imply that female birds may be altering resource allocation to their female offspring in multiple ways.

  13. Generating the Rice Bowl

    Rice is thought to have been domesticated around 10,000 years before it developed into one of our most important food crops. While examining archaeological sites in the lower Yangtze basin, Fuller et al. (p. 1607; see the news story by Balter) were able to determine the timing of rice farming in Asia and showed that, like the taming of wheat, rice domestication developed over a long period. They identified domesticated rice on the basis of its nonshattering phenotype and showed that it gradually replaced wild-gathered plants in the diet.