Editors' Choice

Science  21 Aug 2015:
Vol. 349, Issue 6250, pp. 839
  1. Materials Science

    When wrinkling is a good thing

    1. Marc S. Lavine

    Hierarchical wrinkles made by three generations of sequential wrinkling

    PHOTO: W.-K. LEE ET AL.

    A common feature of gecko feet, which show strong adhesion to many surfaces, and the lotus leaf, which can repel water, is a hierarchical, patterned surface that extends across many length scales with controlled regions of order and disorder. Textured surfaces can be synthetically mimicked, but can require complex lithographic methods to make. Lee et al. use a hierarchical wrinkling approach to achieve large-scale patterning, where both the wavelength and orientation of previous-generation wrinkles can be preserved and built upon. Reactive ion etching creates a skin layer on a polystyrene substrate, leading to wrinkling. By adjusting the etching time, they control the wavelength of the wrinkles, with the orientation tuned by prestretching the substrate in one or two directions.

    Nano Lett. 10.1021/acs.nanolett.5b02394 (2015).

  2. Membrane Proteins

    Probing the activity of two proteases

    1. Valda Vinson

    Presinilin (PS), the transmembrane catalytic subunit of the enzyme γ-secretase, is a drug target of high interest. This is because it cleaves both amyloid precursor protein, which is implicated in Alzheimer's disease, and Notch, a protein involved in several cancers. How potential therapeutics may affect related proteins, such as signal peptide peptidase (SPP), an enzyme that has an active site similar to that of PS, is unclear. To investigate this, Gertsik et al. designed photolabeled molecular probes that targeted different parts of the catalytic subpockets of the enzymes. Comparing the labeling profiles of the probes revealed important similarities and differences between the two enzymes. Scientists should take into account such cross-talk as drug development proceeds.

    ACS Chem. Biol. 10.1021/acschembio.5b00321 (2015).

  3. Microbial Communities

    Abundant microbes hiding in plain sight

    1. Nicholas S. Wigginton

    Natural microbial communities are frustratingly complex—even with the advent of powerful metagenomic tools. Overlooked abundant organisms often result in an incomplete view of the metabolic processes that affect major geochemical cycles. Hug et al. developed a subsampling metagenomic assembly technique which, when combined with metaproteomics, reveals a preponderance of highly abundant, novel microbial lineages in subsurface sediments at an old uranium mill tailings site. These organisms cycle carbon, nitrogen, and sulfur through unanticipated pathways. For example, despite low ammonium concentrations in the aquifer, the most abundant community member in the sediment is an ammonium-oxidizing archaeon that partially utilizes ammonium produced by nitrate-reducing bacteria.

    Environ. Microbiol. 17, 10.1111/1462-2920.12930 (2015).

  4. Neuroimmunology

    For females, a different path to pain

    1. Kristen L. Mueller

    The immune cells underlying pain responses may differ between males and females

    IMAGE: H. HUANG ET AL. NAT. STRUCT. MOL. BIOL. (13 JULY 2015) © NATURE PUBLISHING GROUP

    Chronic pain affects more women than men. To better understand why, Sorge et al. compared the mechanisms that underlie neuropathic pain in male and female mice. Previous studies suggested that immune cells called microglia trigger pain sensitivity in response to nerve injury. Surprisingly, blocking microglia genetically or pharmacologically reduced pain in male but not in female mice. This sex-specific response depended on testosterone—blocking microglia alleviated pain in testosterone-treated females but not in castrated mice. Lymphocytes, rather than microglia, appeared to promote pain in female mice. These results suggest that scientists may need to examine sex-specific responses when testing new treatments for pain and other neurological diseases involving immune cells.

    Nat. Neurosci. 18, 1081 (2015).

  5. Genetics

    Copying chromatin to ensure identity

    1. Guy Riddihough

    Structure of the MCM2 histone binding domain–histones H3–H4 tetramer complex

    IMAGE: WAVEBREAKMEDIA/ISTOCK

    When cells divide, they must replicate both their DNA sequence and the chromatin state of their genome to maintain their identity. Huang et al. use structural and biochemical analyses to show how a central component of the human DNA replication machinery, the minichromsome maintenance (MCM) helicase, helps chaperone histones (proteins that package DNA into structures called nucleosomes) from old nucleosomes disassembled ahead of the replication fork to new ones formed behind the fork. The MCM2 subunit works with another histone chaperone, ASF1, to bind both old and new histones, together with variant histones, such as those from the centromeres. In this way, the cell likely ensures the accurate copying of chromatin as well as DNA.

    Nat. Struct. Mol. Biol. 10.1038/nsmb.3055 (2015).

  6. Genetics

    How starving affects you and yours

    1. Laura M. Zahn

    Malnourished children are at higher risk for type 2 diabetes, cancer, and cardiovascular disease later in life. Some scientists hypothesize that this is because early-life experiences prime the body for such encounters later in life. Jobson et al. used the roundworm Caenorhabditis elegans to study this phenomenon. They observed that worms starved early in life were smaller and produced fewer offspring compared to normally fed worms. But the effects did not stop there: Progeny and grandprogeny of starved parents could better resist starvation, and resistance to heat stress persisted for three generations. These results suggest that at least in worms, early stress may be adaptive in an unpredictable environment.

    Genetics 10.1534/genetics.115.178699 (2015).

  7. Education

    What does one know and not know?

    1. Melissa McCartney

    To demonstrate understanding, students need to answer questions correctly, as well as understand why those answers are correct. Lindsey and Nagel examine this metacognition, specifically students' ability to differentiate between questions for which they know the answer and questions that they cannot correctly answer. A knowledge survey mimicking a final exam was used to collect student data. Analysis at the level of students' overall scores showed that students in the lower third of the class misjudged their abilities, whereas students in the top third were better calibrated. However, at the level of individual questions, there was no difference between student level and the ability to identify questions they could answer correctly, suggesting that students at all levels could benefit from metacognitive awareness training.

    Phys. Rev. 10.1103/physrevstper.11.020103 (2015).

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