This Week in Science

Science  25 Nov 2016:
Vol. 354, Issue 6315, pp. 1016
  1. Biosensors

    Better health? Prepare to sweat

    1. Caitlin Czajka

    A flexible electronic microfluidic biosensor

    CREDITS (FROM TOP): DE BAKKER ET AL.; KOH ET AL.

    Tracking heart rate, calories, and steps with wearable technology is a popular way to monitor general health and fitness. Koh et al. take wearable technology one step further by developing a flexible microfluidic device that collects and analyzes sweat. Colorimetric readouts and integrated smartphone image capture detected pH, lactate, glucose, and chloride ion concentrations in sweat while the device was stuck to the skin during a controlled cycling test. Results were comparable to conventional analyses, and the devices remained functional during an outdoor endurance bicycle race. Such microfluidic devices could be used during athletic or military training and could be adapted to test tears, saliva, or other bodily fluids.

    Sci. Transl. Med. 8, 366ra165 (2016).

  2. Geophysics

    Mega-earthquakes go the flat way

    1. Brent Grocholski

    Megathrust faults in subduction zones cause large and damaging earthquakes. Bletery et al. argue that certain geometric features of the subduction zones relate to earthquake size. The key parameter is the curvature of the megathrust. Larger earthquakes occur where the subducting slab is flatter, providing a rough metric for estimating where mega-earthquakes may occur in the future.

    Science, this issue p. 1027

  3. Catalysis

    Tuning nanoparticle strain

    1. Phil Szuromi

    The catalytic activity of metals in heterogeneous catalysts can be altered by applying strain, which changes the crystalline lattice spacing and modifies the metal's electronic properties. Wang et al. show how particles of cobalt oxide, a positive electrode for lithium batteries, can expand or contract with charging and transfer strain to adsorbed platinum nanoparticles. For the oxygen reduction reaction used in fuel cells, compressive strain boosted activity by 90%, and tensile strain decreased it by 40%.

    Science, this issue p. 1031

  4. Biocatalysis

    Bringing carbon-silicon bonds to life

    1. Nicholas S. Wigginton

    Organic compounds containing silicon are important for a number of applications, from polymers to semiconductors. The catalysts used for creating carbon-silicon bonds, however, often require expensive trace metals or have limited lifetimes. Borrowing from the ability of some metallo-enzymes to catalyze other rare carbene insertion reactions, Kan et al. used heme proteins to form carbon-silicon bonds across a range of conditions and substrates (see the Perspective by Klare and Oestreich). Directed evolution experiments using cytochrome c from Rhodothermus marinus improved the reaction to be 15 times more efficient than industrial catalysts.

    Science, this issue p. 1048; see also p. 970

  5. Memory Research

    Protecting memories from stress

    1. Peter Stern

    It is widely accepted that stress has a negative impact on memory retrieval. But specific approaches to learning can counteract this effect. Smith et al. found that when memory was tested immediately after the onset of stress, stress effects were reduced. Furthermore, when subjects learned novel material by using a highly effective learning technique involving practice tests, their memory was also protected against the negative effects of stress.

    Science, this issue p. 1046

  6. Pharmacology

    Targeting the ligand in hypophosphatemia

    1. Leslie K. Ferrarelli

    Patients with chronic kidney disease can have too much circulating FGF-23 (fibroblast growth factor 23). This results in too little circulating phosphate (hypophosphatemia) and the bone-softening disorder rickets. Because available FGF-23 receptor–targeting molecules are not clinically useful, Xiao et al. sought to identify ligand-binding compounds. Their lead compound reduced FGF-23 serum levels and partially reversed hypophosphatemia in a mouse model. Thus, targeting the ligand, rather than the receptor, may be a therapeutic option for hypophosphatemia.

    Sci. Signal. 9, ra113 (2016).

  7. Behavioral Immunology

    Status alters immune function in macaques

    1. Laura M. Zahn

    Rhesus macaques experience variable levels of stress on the basis of their position in the social hierarchy. To examine how stress affects immune function, Snyder-Mackler et al. manipulated the social status of individual macaques (see the Perspective by Sapolsky). Social status influenced the immune system at multiple levels, from immune cell numbers to gene expression, and altered signaling pathways in a model of response to infection. Macaques possess a plastic and adaptive immune response wherein social subordination promotes antibacterial responses, whereas high social status promotes antiviral responses.

    Science, this issue p. 1041; see also p. 967

  8. Cold Atoms

    Making perfect atomic arrays

    1. Jelena Stajic

    Arrays of atoms can be a useful resource for quantum information. However, loading atoms into arrays is typically a stochastic process, which leads to imperfections. Two groups have now performed defect-free assembly of atoms into arrays (see the Perspective by Regal). The researchers first loaded the atoms stochastically and imaged the system. They then shuttled the atoms around to form perfect arrays. Barredo et al. worked with two-dimensional arrays, creating a variety of spatial configurations. Endres et al. manipulated atoms along a line. By further cooling down the atoms and generating interactions among them, the techniques may also find use in quantum simulation.

    From random to ordered arrays

    PHOTO: BARREDO ET AL.

    Science, this issue p. 972, p. 1021; see also p. 1024

  9. Autophagy

    Open sesame!

    1. Stella M. Hurtley

    The autophagosome is a double-membraned intracellular structure involved in the disposal of damaged or defunct organelles. Autophagosome formation requires a number of autophagy-related (ATG) proteins. Among them, the key conjugation systems ATG8 and ATG12 are widely exploited in the detection of autophagy in many organisms. However, their precise function in autophagy remains unknown. Tsuboyama et al. identified an unexpected role of ATG3, an important enzyme in the ATG conjugation systems, in efficient degradation and opening of the inner autophagosomal membrane after fusion with lysosomes (see the Perspective by Levine). Their live-imaging system revealed the entire life of an autophagosome in mammalian cells.

    Science, this issue p. 1036; see also p. 968

  10. Human Development

    Digital reconstruction of human development

    1. Beverly A. Purnell

    The detailed morphology of human development has intrigued scientists and the medical field alike. However, the scarcity of specimens hampers detailed mapping of tissue architecture. Furthermore, inaccuracies in the description of human development have crept into textbooks from observations of animal models that are extrapolated to humans. By mapping normal developmental processes and patterns, such as the growth and relative placement of organs, congenital anomalies can be better understood. de Bakker et al. generated interactive three-dimensional digital reconstructions based on the Carnegie collection of histologically sectioned human embryos spanning the first 2 months of gestation. These interactive models will serve as educational and scientific resources for normal and abnormal human development.

    Science, this issue p. 10.1126/science.aag0053

  11. Cell Reprogramming

    For cell reprogramming, context matters

    1. Paula A. Kiberstis

    Differentiated cells in a culture dish can assume a new identity when manipulated to express four transcription factors. This “reprogramming” process has sparked interest because conceivably it could be harnessed as a therapeutic strategy for tissue regeneration. Mosteiro et al. used a mouse model to study the signals that promote cell reprogramming in vivo. They found that the factors that trigger reprogramming in vitro do the same in vivo; however, they also inflict cell damage. The damaged cells enter a state of senescence and begin secreting certain factors that promote reprogramming, including an inflammatory cytokine called interleukin-6. Thus, in the physiological setting, cell senescence may create a tissue context that favors reprogramming of neighboring cells.

    Science, this issue p. 10.1126/science.aaf4445

  12. Epidemiology

    Increasing viral threats from mosquitoes

    1. Julia Fahrenkamp-Uppenbrink

    Viral diseases such as dengue, Zika, and yellow fever are transmitted by the mosquito Aedes aegypti. In a Perspective, Powell highlights recent changes in the global distribution and genetic characteristics of this insect. The two main genetic subtypes of the mosquito have historically differed in their breeding and host preferences and were found in different geographic regions. However, they are now interbreeding in several locations and spreading into new areas. These changes are putting large human populations at risk of diseases against which they will have no immune defenses.

    Science, this issue p. 971