Editors' Choice

Science  20 Jun 2014:
Vol. 344, Issue 6190, pp. 1355
  1. Ion Transport

    Solving the mystery of iodine uptake

    1. Valda Vinson

    Iodine ion transport by the NIS protein.

    PHOTO: ILLUSTRATION: V. ALTOUNIAN/SCIENCE

    The thyroid gland produces iodine-containing hormones that regulate metabolism. The cell membrane protein NIS (sodium/iodine symporter) transports iodine into thyroid cells, but because iodine concentrations outside of the cell are so low, how it does so is a mystery. The key? Moving two sodium ions along with the iodine ion, Nicola et al found. NIS also does not bind sodium very tightly, but the high concentrations of sodium outside the cell allow one sodium ion to bind. This binding increases the affinity of NIS for a second sodium ion and also for iodine. With the three ions bound, NIS changes its conformation so that it opens to the inside of the cell, where the sodium concentration is low enough for NIS to release its sodium ions. When the sodium goes away, so does NIS's affinity for iodine, leading NIS to release it.

    Nat. Commun. 10.1038/ncomms4948 (2014).

  2. Disease Mechanisms

    An airborne agent of heart disease?

    1. Barbara R. Jasny

    Kawasaki disease is the most common cause of acquired heart disease in children, but even now—40 years after its discovery—doctors still don't know its cause. Infectious and environmental agents are both possibilities. Rodó et al. compared daily Kawasaki disease case records in Japan with models of regional air trajectories. Spikes in disease incidence, they found, occurred when the wind blew from an agricultural region in northeastern China. Aerosol samples identified a high abundance of Candida, a fungus. Although the results are only a correlation, they support an existing model suggesting that genetically susceptible children may develop the disease when a windborne toxin or environmental agent triggers an aberrant immune response.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1400380111 (2014). Nat. Genet. 10.1038/ng.2982 (2014)

  3. Metabolic Genetics

    Genetic variation affects blood metabolites

    1. Laura M. Zahn

    Genetic variation influences human metabolism dramatically. Understanding the process could help researchers identify drugs and develop better treatments for complex diseases. In a study of over 7000 adults, Shin et al. reconstructed metabolic pathways by combining genetics with metabolomics, the study of small molecules (aka metabolites) in biological systems. They identified 145 genetic loci, 84 previously unidentified, that they predicted would affect a wide range of biological functions. These 145 genetic loci were connected in a network to 400 biochemically relevant blood metabolites, forming an atlas of metabolites in the blood. Identifying these genetic variants that affect blood metabolites helps us gain a better understanding of human biology and potential treatments for disease.

    Nat. Genet. 10.1038/ng.2982 (2014).

  4. Paleoclimate

    Seasonal rainfall and Indonesian vegetation

    1. H. Jesse Smith

    Both gradual and abrupt changes in rainfall—similar in many ways to those happening today—had dramatic effects on the vegetation of Indonesia over the past 25,000 years. Dubois et al. report that variations in the seasonality of rainfall there, and the resulting water stress during the dry season, caused large swings in the balance between grasslands and forests. Vegetation type depended more on the depth of seasonal dry cycles than on the amount of annual rainfall, they found. These results, obtained by analyzing the stable isotopic composition of fatty acids produced by vascular plants and preserved in marine sediments, reflect the importance of the monsoonal precipitation that's so vital to Indonesian agriculture and human well-being.

    Nat. Geosci. 10.1038/ngeo2182 (2014).

  5. Green Chemistry

    Making plastic bottles more renewable

    1. Phil Szuromi

    Plastic bottle made from all-green stock.

    PHOTO: © MAXAL TAMOR/ALAMY

    All of the components of the plastic used to make clear soda bottles now can be supplied by renewable materials. The polymer polyethylene terphthalate is made from two monomers, ethylene and terphthalic acid (PTA). Chemists already can make ethylene from ethanol produced from plants, but PTA is made by oxidizing p-xylene, a petroleum derivative. Pachero and Davis show that a chemical derived on a commercial scale from biomass, 5-hydroxymethylfurfural (HMF), can be converted to PTA with the help of a catalyst called tin-beta. This process opens a route to more environmentally friendly plastic bottle manufacture.

    Proc. Natl. Acad. Sci U.S.A. 10.1073/pnas.1408345111 (2014).

  6. Physics

    A second hump in a superconducting dome

    1. Jelena Stajic

    Pure strontium titanate (SrTiO3) does not conduct electricity, but adding tiny amounts of impurities can turn it into a perfect conductor: a superconductor. Lin et al. found that, for a particular concentration of extra electrons introduced by adding Nb to the samples, the temperature at which SrTiO3 becomes superconducting (Tc) has a maximum. This concentration coincides with the state when the electrons have filled up one energy band of the material and are just starting to fill up another. By measuring the electrical resistivity of the samples, they found that the overall shape of the Tc dependence on the electron concentration was a two-humped dome. Unlike superconducting domes in other materials, the base of the dome was quite broad and spanned a range of over three orders of magnitude of carrier concentration.

    Phys. Rev. Let. 112, 207002 (2014).

  7. Polar Ecology

    Iceberg scours alter seafloor diversity

    1. CG

    The ocean seabed is a patchwork quilt of colors and species. But along the West Antarctic Peninsula, increased iceberg activity—due to climate change and fewer days of frozen seas—is reducing sea floor biodiversity. Icebergs scouring the sea floor temporarily destroy habitat; different species recover at different rates. Barnes et al. examined spatial distribution, diversity, interactions between and within species, and ice scour hits near Rothera Research Station from 1997 to 2013. One species, Fenestrulina rugula, was quickest to recover; it now dominates, and is involved in, 96% of all interactions. Such reduced diversity could mean more vulnerability to invasive species.

    Curr.Biol. 10.1016/j.cub.2014.04.040(2014).

  8. Physiology

    Gill-on-a-chip illuminates evolution

    1. Guy Riddihough

    Gill lamellae of the cichlid fish.

    PHOTO: DENNIS KUNKEL MICROSCOPY, INC/VISUALS UNLIMTED, INC.

    Fish gills are natural microfluidic devices that evolution has optimized to extract oxygen from water. The spacing between the lamellae, the tiny protrusions that cover gill filaments, varies little between fish of wildly different sizes, which suggests that this spacing is important for gill function. To test this, Park et al. developed a mathematical model for oxygen transfer across lamellae. Indeed, they found, lamellae spacing is critical for gill function, as is the way fish pump water through their gills. The researchers then tested their model against an artificial gill—a microfluidic chip where oxygen diffuses across synthetic membranes. When they varied the distance between the membranes, the artificial gill extracted the most oxygen with membrane spacing similar to that of lamellae in fish gills.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1403621111 (2014).

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