Editors' Choice

Science  11 Sep 2015:
Vol. 349, Issue 6253, pp. 1179
  1. Climate

    Explaining the last glacier retreat

    1. Julia Fahrenkamp-Uppenbrink

    “Erratic” boulders deposited by a receding glacier

    PHOTO: © DAVID ROBERTSON/ALAMY STOCK

    Between 19,000 and 11,500 years ago, glaciers around the globe retreated as Earth emerged from the last glacial period. Efforts to identify the main drivers of this retreat have been hampered by dating uncertainties. Shakun et al. have recalculated the ages of over 1000 glacial boulders from almost 200 sites around the world, using an improved calibration that provides more accurate dates. They find that although there are regional variations, most glacier retreats coincided with the rise in atmospheric carbon during the deglaciation. The high sensitivity of alpine glaciers to carbon dioxide increases has implications for future glacier loss as a result of climate change.

    Nat. Commun. 10.1038/ncomms9059 (2015).

  2. Microbiology

    Stomach microbe finds a safe haven

    1. Stella M. Hurtley

    Helicobacter pylori follow a urea trail to the relative safety of the gut epithelium

    PHOTO: SPL/SCIENCE SOURCE

    Helicobacter pylori causes stomach ulcers and is linked to gastric cancer. How does this microbe survive in the destructive environment of the stomach? Huang et al. looked at how H. pylori manages to make its way to the gastric epithelium, where it can reside relatively unscathed by the stomach's defenses. H. pylori express a protein chemoreceptor, TlpB, that sniffs out urea released by the gut epithelium. The bugs follow a urea trail to the epithelium and simultaneously degrade the urea to generate ammonia and bicarbonate, which can help to buffer the microbe from the stomach acids. The authors watched how the bacteria locate and swim toward epithelia within seconds, attracted by minute amounts of urea.

    Cell Host Microbe 18, 147 (2015).

  3. Protein Design

    Switching off protein production

    1. Valda Vinson

    Controlling protein production is desirable, but current methods are complex, inefficient, difficult to generalize, or not quickly reversible. Chung et al. describe a small-molecule–assisted shutoff (SMASh) tag that is genetically added to a target protein and allows reversible shutoff of various proteins in multiple cell types. The tag includes a site that is cut by a protease and a degron sequence that targets the protein for rapid destruction. Active protease cuts the tag from newly synthesized protein so that it does not disrupt protein function. However, inhibiting the protease with a clinically approved drug protects the tag, and the degron sequence causes the protein to be rapidly degraded. Stopping the drug restores protein production.

    Nat. Chem. Biol 10.1038/nchembio.1869 (2015).

  4. Materials Science

    Brushing up on being soft and squishy

    1. Marc S. Lavine

    Polymer gels can be thought of as a netlike structure of cross-linked linear polymer chains swollen with solvent. Because these materials are mostly liquid, they can be quite soft and squishy, but this means that solvent loss, which makes the gels sticky, also is a concern. Cai et al. fabricated very long poly(dimethylsiloxane) chains with a bottle-brush structure: long backbone macromolecules heavily decorated with short side chains (a bit like a hairy caterpillar), which prevent the long chains from entangling. When cross-linked, these chains formed soft gellike materials with a tunable elastic modulus that was dependent on the crosslink density.

    Adv. Mater. 10.1002/adma.201502771 (2015).

  5. Metabolomics

    Terroir quantified

    1. Pamela J. Hines

    Wines are characterized not only by year but by vineyard. Anesi et al. used chromatography and microarrays to analyze the metabolomes of one variety of the Corvina grape variety grown in different settings in Italy. The study spanned 3 years in order to average effects due to variation in temperature, sunlight, and rainfall. Shifts in the composition of volatile and nonvolatile compounds that correlate with altitude, viticultural practices, and characteristics of the soil revealed the signatures attributable to terroir.

    BMC Plant Biol. 10.1186/s12870-015-0584-4 (2015).

  6. Neurodevelopment

    Brain development hamstrung

    1. Pamela J. Hines

    Mutations in a zinc-finger transcription factor known as Zic2 cause problems in cortical development and can result in schizophrenia symptoms. Studying embryonic mice, Murillo et al. show that this protein supports migrations of several types of neural cells during brain development. The loss of Zic2 hobbled Cajal-Retzius cells, which lay the groundwork for further brain development, as well as cells destined to build key relay and integrative centers in the brain. Normal in number, the stranded Cajal-Retzius cells release their signaling molecule reelin in the wrong places. The migration problems may also range through neural development, affecting cells from the prechordal plate to the neural crest that emigrate from the neural tube.

    J. Neurosci. 35, 32 (2015).

  7. Education

    Assessing chemistry one class at a time

    1. Melissa McCartney

    Before changes in a curriculum can be proposed, it is necessary to assess the current state of the course. Fox and Roehrig did exactly that when surveying undergraduate physical chemistry courses in the United States. Data were collected about issues such as depth versus breadth of content, types of assessments, teacher preparation, and beliefs about the challenging nature of physical chemistry, allowing more-informed decisions to be made about the future of physical chemistry education. Two main themes uncovered by the survey, “how can instructors clearly translate learning goals into assessments” and “how can instructors gain more teacher preparation experience,” are relevant to all science disciplines and can be used as a starting point for future science education research.

    J. Chem. Edu. 10.1021/acs.jchemed.5b00070 (2015).