This Week in Science

Science  15 Apr 2016:
Vol. 352, Issue 6283, pp. 304
  1. Coral Reefs

    Bleaching of the Great Barrier Reef

    1. Caroline Ash

    Coral resilience to high temperatures is limited.

    PHOTO: PETER MUMBY

    The Australian Great Barrier Reef (GBR) is one of Earth's most extraordinary natural wonders, but it is vulnerable to climate change. Ainsworth et al. have tracked the effects of three decades of increasing heat stress on coral organisms. In the past, pulses of elevated temperatures that presaged hot seasons stimulated the acclimation of coral organisms and resilience to thermal stress. More recently, temperature hikes have been severe and precluded acclimation. The result has been increasing bleaching and death; notably extreme during 2016 in the wake of El Niño.

    Science, this issue p. 338

  2. Cell Biology

    Repairing tears in the nuclear envelope

    1. Stella M. Hurtley

    The nuclear envelope segregates genomic DNA from the cytoplasm and regulates protein trafficking between the cytosol and the nucleus. Maintaining nuclear envelope integrity during interphase is considered crucial. However, Raab et al. and Denais et al. show that migrating immune and cancer cells experience frequent and transitory nuclear envelope ruptures when they move through tight spaces (see the Perspective by Burke). The nuclear envelope reseals rapidly during interphase, assisted by components of the ESCRT III membrane-remodeling machinery.

    Science, this issue pp. 359 and 353; see also p. 295

  3. Zika Virus Outbreak

    Zika virus genomes from Brazil

    1. Caroline Ash

    The Zika virus outbreak is a major cause for concern in Brazil, where it has been linked with increased reports of otherwise rare birth defects and neuropathology. In a phylogenetic analysis, Faria et al. infer a single introduction of Zika to the Americas and estimated the introduction date to be about May to December 2013—some 12 months earlier than the virus was reported. This timing correlates with major events in the Brazilian cultural calendar associated with increased traveler numbers from areas where Zika virus has been circulating. A correlation was also observed between incidences of microcephaly and week 17 of pregnancy.

    Science, this issue p. 345

  4. Interstellar Dust

    Cassini detects interstellar dust grains

    1. Keith T. Smith

    The interstellar medium contains an array of small solid particles known as dust grains. Altobelli et al. used the dust analyzer on the Cassini probe to detect 36 interstellar dust grains as they passed by Saturn, and they measured the grains' elemental abundances. The results show that, remarkably, these grains lack carbon-bearing compounds and have been homogenized in the interstellar medium into silicates with iron inclusions.

    Science, this issue p. 312

  5. Biomaterials

    Engineering a healing immune response

    1. Kristen L. Mueller

    Infections, surgeries, and trauma can all cause major tissue damage. Biomaterial scaffolds, which help to guide regenerating tissue, are an exciting emerging therapeutic strategy to promote tissue repair. Sadtler et al. tested how biomaterial scaffolds interact with the immune system in damaged tissue to promote repair (see the Perspective by Badylak). Scaffolds derived from cardiac muscle and bone extracellular matrix components trigger a tissue-reparative T cell immune response in mice with injured muscles.

    Science, this issue p. 366; see also p. 298

  6. Structural Biology

    Blueprint for a macromolecular machine

    1. Valda Vinson

    Nuclear pore complexes (NPCs) consist of around 1000 protein subunits, are embedded in the membrane that surrounds the nucleus, and regulate transport between the nucleus and the cytoplasm. Although the overall shape of NPCs is known, the details of this macromolecular complex have been obscure. Now, Lin et al. have reconstituted the pore components, determined the interactions between them, and fitted them into a tomographic reconstruction. Kosinski et al. have provided an architectural map of the inner ring of the pore.

    Science, this issue pp. 10.1126/science.aaf1015 and 363

  7. Thermodynamics

    Making a teeny tiny engine

    1. Jelena Stajic

    Steam locomotives, cars, and the drinking bird toy all convert heat into useful work as it cycles between two reservoirs at different temperatures. Usually, the working substance where the heat-work conversion occurs is a liquid or a gas, consisting of many molecules. Roβnagel et al. have made a working substance of a single calcium ion in a tapered ion trap. A laser-cooling beam plays the part of a cold reservoir for the calcium ion, and in turn, electric field noise acts as a hot reservoir.

    Science, this issue p. 325

    Heat engines can also be made from single atoms.

    PHOTO: © VPC PHOTO/ALAMY STOCK PHOTO
  8. Cancer

    Adding fuel to the fire

    1. Yevgeniya Nusinovich

    Antioxidant drugs used to treat cancer can cause undesirable side effects. Diabetic patients are at increased risk of developing cancer, and Wang et al. show that drugs with antioxidant properties used to treat diabetes all accelerated metastasis in mouse models of cancer. Although not yet tested in human patients, it might be prudent to exercise caution when prescribing these types of drugs to patients with an increased risk of developing cancer.

    Sci. Transl. Med. 8, 334ra51 (2016).

  9. Organometallics

    Where Pd and B meet in Suzuki coupling

    1. Jake Yeston

    The Suzuki-Miyaura reaction is widely used to form carbon-carbon bonds. It operates by transferring a carbon center from boron to palladium, although the handoff itself happens too quickly to see. Thomas and Denmark have caught sight of the previously elusive intermediate complexes linking palladium to boron through an intervening oxygen. Using low-temperature nuclear magnetic resonance spectroscopy, they characterized the intermediate structures just before the carbon transfer event.

    Science, this issue p. 329

  10. Environment

    Where do all the mine wastes go?

    1. Julia Fahrenkamp-Uppenbrink

    Mining operations have led to vast accumulations of toxic waste in nearly every country. As Hudson-Edwards explains in a Perspective, mining wastes pose substantial risks to ecosystem and human health. The environmental impacts are particularly severe when tailings dams fail and large amounts of toxic, corrosive, or radioactive materials spill into river basins. Weathering and wind can also redistribute mine wastes, with harmful consequences. Although environmental protection legislation has helped, we need to better define the dynamics of mine wastes to control their environmental impacts.

    Science, this issue p. 288

  11. Photovoltaics

    Surveying the solar cell landscape

    1. Ian S. Osborne

    The rate of development and deployment of large-scale photovoltaic systems over recent years has been unprecedented. Because the cost of photovoltaic systems is only partly determined by the cost of the solar cells, efficiency is a key driver to reduce the cost of solar energy. There are several materials systems being explored to achieve high efficiency at low cost. Polman et al. comprehensively and systematically review the leading candidate materials, present the limitations of each system, and analyze how these limitations can be overcome and overall cell performance improved.

    Science, this issue p. 10.1126/science.aad4424

  12. Structural Biology

    An RNA methylase caught in the act

    1. Valda Vinson

    RNA methylation is important in RNA function and in antibiotic resistance. The RNA methylase RlmN is a dual-specificity enzyme that can act on ribosomal and transfer RNA (tRNA). RlmN is a radical S-adenosylmethionine (SAM) enzyme, which produces a protein/RNA cross-linked intermediate. Schwalm et al. determined the structure of RlmN cross-linked to a tRNA substrate and found that the enzyme recognizes the overall shape of the tRNA. Then it remodels the anticodon region to access the base that it methylates. The remodeling activity is likely to be key to the enzyme's dual specificity.

    Science, this issue p. 309

  13. Molecular Magnetism

    Stable magnets from single atoms

    1. Phil Szuromi

    An important goal in molecular magnetism is to create a permanent magnet from a single atom. Metal atoms adsorbed on surfaces can develop strong magnetization in an applied field (paramagnetism). Donati et al. show that single holmium atoms adsorbed on a magnesium oxide film grown on a silver substrate show residual magnetism for temperatures up to 30 K and bistabilty that lasts for 1500 s at 10 K (see the Perspective by Khajetoorians and Heinrich). The atom avoids spin relaxation by a combination of quantum-state symmetry and by the oxide film preventing the spin from interacting with the underlying metal via tunneling.

    Science, this issue p. 318; see also p. 296

  14. Hydrogen Bonding

    Quantum effects in single hydrogen bonds

    1. Phil Szuromi

    Hydrogen bonds are a combination of electrostatics with a nuclear quantum contribution arising from the light mass of hydrogen nuclei. However, the quantum states of hydrogen nuclei are extremely sensitive to coupling with local environments, and these effects are broadened and averaged with conventional spectroscopic or diffraction techniques. Guo et al. show that quantum effects change the strength of individual hydrogen bonds in water layers adsorbed on a salt surface. These effects are revealed in inelastic tunneling spectra obtained with a chlorine-terminated scanning tunneling microscope tip.

    Science, this issue p. 321

  15. Electrochemistry

    Modulating metal oxides

    1. Phil Szuromi

    The more difficult step in fuel cells and water electrolysis is the oxygen evolution reaction. The search for earth-abundant materials to replace noble metals for this reaction often turns to oxides of three-dimensional metals such as iron. Zhang et al. show that the applied voltages needed to drive this reaction are reduced for iron-cobalt oxides by the addition of tungsten. The addition of tungsten favorably modulates the electronic structure of the oxyhydroxide. A key development is to keep the metals well mixed and avoid the formation of separate phases.

    Science, this issue p. 333

  16. Forest Ecology

    Carbon trading between adult trees

    1. Andrew M. Sugden

    Competition between individual plants for resources is well known, but sharing of resources may also occur. Klein et al. observed tree-to-tree carbon shuttling between roots of tall trees in a mixed temperate forest in Switzerland (see the Perspective by van der Heijden). By applying stable carbon isotope labeling to individual tree canopies, they show that up to 40% of the carbon in the fine roots of one individual may be derived from photosynthetic products of a neighbor. Carbon transfer of this kind, mediated by plant-associated fungi, or mycorrhizae, in the soil, has been reported on a smaller scale in seedlings, but not before in trees.

    Science, this issue p. 342; see also p. 290

  17. Malaria Drugs

    Transmission blocked by drug resistance

    1. Caroline Ash

    Resistance to the antimalarial drug atovaquone might prove to be this parasite's weak spot. Resistance develops rapidly via mutations in the drug's target: the parasite's mitochondrial cytochrome b complex. Goodman et al. have discovered that although resistant Plasmodium berghei parasites persist in mice, in blood-sucking malarial mosquitoes, the mutations disable female parasites too much for them to reproduce. The human-specific Plasmodium falciparum can only be investigated experimentally in mosquitoes, but a similar effect was seen. Thus, atovaquone-resistant parasites cannot be transmitted to another mammal or person.

    Science, this issue p. 349

  18. Developmental Disorders

    A disease-causing G protein switch

    1. Leslie K. Ferrarelli

    Mutations in components of the endothelin signaling pathway prevent the nervous system from developing properly, which results in the craniofacial defects characteristic of auriculocondylar syndrome (ACS). Some ACS patients have mutations in Gαi3, a G protein subunit that is not normally part of the endothelin signaling pathway. Marivin et al. found that the Gαi3 mutations associated with ACS enabled Gαi3 to bind inappropriately to an endothelin receptor and block the binding of another G protein. Because the Gαi3 mutants lacked enzymatic activity, they prevented the receptor from signaling.

    Sci. Signal. 9, ra37 (2016).