Editors' Choice

Science  05 Jun 2015:
Vol. 348, Issue 6239, pp. 1103
  1. Materials Science

    Faster ways to flexible electronics

    1. Marc S. Lavine

    Semiconductor chips attached to a flexible, stretchable support

    PHOTO: S.-C. PARK ET AL. ADVANCED MATERIALS (12 MAY 2015) © 2015 JOHN WILEY & SONS, INC.

    Stretchable electronics that combine both inorganic and organic parts require processing methods compatible with both types of materials. Writing semiconductors directly onto flexible substrates is possible only at low temperatures. If one fabricates the semiconductors first, precise alignment steps are needed, including deposition of the interconnects. Park et al. developed a process of directed self-assembly where light-emitting diodes (LEDs) can be fluidically deposited onto a stretchable substrate, so that they bond to regions that are isolated from deformation. The bottom substrate contained regions of solder that directed the LED assembly. A top conductive layer was designed for rapid attachment without critical alignment. Thus, flexible solid-state lighting could be made in a continuous roll-to-roll process.

    Adv. Mat. 10.1002/adma.201500839 (2015).

  2. Aging

    In search fo an anti-aging drug

    1. Bryan L. Ray

    As organisms age, they accumulate cells that can no longer proliferate. Such cells— termed “senescent”—persist and appear to promote aging by producing and secreting a variety of proteins. Zhu et al. tested whether drugs that inhibit cellular signaling pathways that make senescent cells resistant to stress and cell death could deplete senescent cells in mice. A combination of two drugs that inhibit such pathways selectively killed senescent cells in vitro, improved heart and vascular function in aging mice, and improved symptoms in a mouse model of accelerated aging. Although pinpointing the relevant targets of these drugs is difficult, the studies indicate that selectively targeting senescent cells with small molecules may be feasible.

    Aging Cell 10.1111/acel.12344 (2015).

  3. Evolution

    Maintaining a massive mitochondrial genome

    1. Laura M. Zahn

    Silene noctiflora plants have an unusually large mitochondrial genome

    PHOTO: © FLORALIMAGES/ALAMY

    Even within the same species, flowering plants exhibit extreme differences in genome size, composition, and organization of their mitochondrial genomes. The coding sequence, however, is a different story. Wu et al. sequenced the mitochondrial genome of the plant Silene noctiflora and found that the genome consisted of 54 genes mapping to 59 circular chromosomes of varying size, many of which lacked genes. When compared with an individual from another population, both mitochondrial genomes contained the same number and organization of genes. However, variation was observed in total chromosome number (59 versus 63), suggesting that noncoding sequence had both been lost and gained between the populations but that selection maintains genetic information in the mitochondria.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1421397112 (2015).

  4. Translation

    Special proteins for stressed cells

    1. Guy Riddihough

    Stress, in the form of high temperatures, causes cells to shut down the translation of most messenger RNAs (mRNAs). At the same time, stress activates the synthesis of a small number of proteins needed for cell survival and recovery, but how? To find out, Zhang et al. exposed human tissue culture cells to heat stress and found that they produced an alternative form of the protein MRPL18, which is normally part of mitochondrial ribosomes. When stressed, cells express this alternative form of MRPL18 and incorporate it into cytosolic ribosomes, large protein complexes required for translation. These modified ribosomes can engage and efficiently translate mRNAs needed for stress survival.

    Nat. Struct. Mol. Biol. 22, 404 (2015).

  5. Microbiota

    A new normal for the microbiota

    1. Kristen L. Mueller

    Many surfaces of the human body, including the genital tract, harbor bacteria collectively referred to as the microbiota. Previous studies suggested that a healthy vaginal microbiota is lactobacillus-dominant and has low bacterial diversity. Anahtar et al. now challenge this. Studying young healthy women in South Africa, they identified four clusters of vaginal microbiomes. Only 37% of the women fell into lactobacillus-dominant clusters. The rest had more diverse microbiomes dominated by other genera. One diverse cluster associated strongly with genital inflammation. Because genital inflammation can place women at higher risk for acquiring sexually transmitted infections (STIs), such as HIV, these results suggest that the vaginal microbiome may influence rates of STI acquisition.

    Immunity 42, 965 (2015).

  6. Green Chemistry

    Savvy solvent swaps to make artemisinin

    1. Jake Yeston

    Solvents greatly influence the course of chemical reactions. More indirectly, they constrain the accessible temperature and pressure conditions and frequently constitute the bulk of waste left over when reactions are finished. Amara et al. explored the advantages of using environmentally friendly solvents in the photochemical oxidation process used to make the antimalarial drug artemisinin. In particular, they developed one protocol using liquefied carbon dioxide and another using mixtures of water and either ethanol or tetrahydrofuran. The latter protocol operated at room temperature, and the solvents could be recycled after directly delivering crystallized product.

    Nat. Chem. 7, 10.1038/NCHEM.2261 (2015).

  7. Education

    Review sessions: From passive to active

    1. Melissa McCartney

    Most science lectures begin with a 5- to 10-min review of what was covered previously, but is this time well spent? Using trained observers, Maxwell et al. showed that students lose focus during review sessions, ultimately leading to more time being lost as students attempt to reengage when new material is presented. To alleviate this, a “two-stage” review session, where students work on problems relating to the review material first alone and then in groups, was introduced. Results show that the active review sessions increased student engagement, allowed instructors to immediately know with what content students were or were not struggling, and allowed students to participate in active learning.

    J. Coll. Sci. Teach. 44, 48 (2015).