This Week in Science

Science  03 Mar 2017:
Vol. 355, Issue 6328, pp. 920
  1. Materials Chemistry

    Turning colloidal gold into clathrates

    1. Phil Szuromi

    Nanoscale gold bipyramids can be used in conjunction with programmable assembly to generate clathrate architectures.

    CREDIT: DIERCKS AND YAGHI; LIN ET AL.

    Clathrates contain extended pore structures that can trap other molecules. Lin et al. created colloidal analogs of clathrates in which bipyramidal gold nanoparticles functionalized with DNA molecules assembled into polyhedral clusters to create open-pore structures (see the Perspective by Samanta and Klajn). These clathrate colloidal crystals exhibit extraordinary structural complexity and substantially broaden both the scope and the possibilities provided by DNA-inspired methodologies.

    Science, this issue p. 931; see also p. 912

  2. Optoelectronics

    An on-chip microwave source

    1. Ian S. Osborne

    The active elements of superconducting quantum circuits are typically addressed and controlled using pulses of microwave radiation. The microwaves are usually generated externally and coupled into the circuitry, resulting in rather bulky systems. Cassidy et al. developed an on-chip source of microwaves by using a superconducting Josephson junction inserted in a high-quality microwave cavity. The integrated version should enhance the control capability for manipulating miniaturized quantum circuits.

    Science, this issue p. 939

  3. Social Science

    Indirect military alliances reduce war

    1. Aaron Clauset

    Alliances, even indirect ones, lessen the chances of war between nations.

    CREDIT: PHOTO RESEARCHERS/GETTY IMAGES

    It is remarkable that large-scale military conflict has been more RESEARCH or less absent in the world since the end of World War II. What mechanisms explain this long peace? Li et al. used detailed historical data on military disputes worldwide since 1965 to estimate the network effect of indirect alliances for promoting peace. Nations were less likely to have a military dispute if they were connected in the global network of alliances by one or even two intermediary allies, but not if they were separated any further. This suppression effect was driven primarily by large communities of densely allied nations, the unraveling of which could increase the risk of worldwide conflict.

    Sci. Adv. 10.1126.sciadv.1601895 (2017).

  4. Geochemistry

    Turning up the mantle temperature

    1. Brent Grocholski

    The temperature at which Earth's mantle begins to melt is a long-standing question in geology. Sarafian et al. present a clever set of experiments to determine the impact of small amounts of water on the melting temperature of mantle rock (see the Perspective by Asimow). This allowed them to reinterpret geophysical observations of melting in the mantle and revise estimates of mantle temperature upward. A hotter mantle has a multitude of implications for mantle melting and geodynamic processes.

    Science, this issue p. 942; see also p. 908

  5. DNA Storage

    A reliable and efficient DNA storage architecture

    1. Laura M. Zahn

    DNA has the potential to provide large-capacity information storage. However, current methods have only been able to use a fraction of the theoretical maximum. Erlich and Zielinski present a method, DNA Fountain, which approaches the theoretical maximum for information stored per nucleotide. They demonstrated efficient encoding of information—including a full computer operating system—into DNA that could be retrieved at scale after multiple rounds of polymerase chain reaction.

    Science, this issue p. 950

  6. Plant Science

    Widespread resistance, localized relief

    1. Pamela J. Hines

    Rice blast fungus can devastate a rice harvest. Genes that provide resistance to the fungus usually depress rice yield. Deng et al. analyzed the molecular underpinnings of a rice variant that is resistant to rice blast but still high-yielding (see the Perspective by Wang and Valent). The key locus encodes several R (resistance) genes. One gene confers resistance and is expressed throughout the plant. Another gene fails to confer resistance and is expressed only in pollen and panicles (the rice-producing flower clusters). Because the R proteins function as dimers, heterodimerization in pollen and panicles disables resistance. The plants thus produce smaller but more numerous rice grains, which sustains yield, while the body of the plant resists fungal infection.

    Science, this issue p. 962; see also p. 906

  7. Paleoanthropology

    Morphological mosaics in early Asian humans

    1. Andrew M. Sugden

    Excavations in eastern Asia are yielding information on human evolution and migration. Li et al. analyzed two fossil human skulls from central China, dated to 100,000 to 130,000 years ago. The crania elucidate the pattern of human morphological evolution in eastern Eurasia. Some features are ancestral and similar to those of earlier eastern Eurasian humans, some are derived and shared with contemporaneous or later humans elsewhere, and some are closer to those of Neandertals. The analysis illuminates shared long-term trends in human adaptive biology and suggests the existence of interconnections between populations across Eurasia during the later Pleistocene.

    Science, this issue p. 969

  8. Pain Research

    A pain killer without side effects

    1. Peter Stern

    Opioids are very strong and effective pain killers. However, they also have a range of well-known side effects and can cause addiction. Painful conditions such as inflammation or trauma are often associated with localized tissue acidification. Spahn et al. designed a novel opioid receptor agonist that, unlike clinically used opioids, best activates the receptors in such acidified tissues. In rat models of inflammatory pain, the new drug exerted strong pain relief essentially without the side effects of standard opioids.

    Science, this issue p. 966

  9. Nanotechnology

    Nanowarming improves cryopreservation

    1. Caitlin Czajka

    Organ transplantation is limited by the availability of viable donor organs. Although cryopreservation could extend the time between organ harvest and transplant, the current gold standard for rewarming, convection, leads to cracking and crystallization in samples larger than a few milliliters. Manuchehrabadi et al. rewarmed cells and tissues by radiofrequency inductive heating, using magnetic nanoparticles suspended in a cryoprotectant solution. This nanowarming technique rapidly and uniformly rewarmed cryopreserved fibroblasts, porcine arteries, and porcine heart tissue, yielding tissues with higher viability than those rewarmed by convection.

    Sci. Transl. Med. 9, eaah4586 (2017).

  10. Synthetic Chemistry

    A framework for molecular assembly

    1. Phil Szuromi

    Covalent molecular frameworks are crystalline microporous materials assembled from organic molecules through strong covalent bonds in a process termed reticular synthesis. Diercks and Yaghi review developments in this area, noting the parallels between framework assembly and the covalent assembly of atoms into molecules, as described just over a century ago by Lewis. Emerging challenges include functionalization of existing frameworks and the creation of flexible materials through the design of woven structures.

    Science, this issue p. eaal1585

  11. Ion Channels

    Navigating regulated cell excitation

    1. Valda Vinson

    Voltage-gated sodium (Nav) channels respond to a change in voltage potential by allowing sodium ions to move into cells, thus initiating electrical signaling. Mutations in Nav channels cause neurological and cardiovascular disorders, making the channels important therapeutic targets. Shen et al. determined a high-resolution structure of a Nav channel from the American cockroach by electron microscopy. The structure affords insight into voltage sensing and ion permeability and provides a foundation for understanding function and disease mechanism of Nav and the related Cav ion channels.

    Science, this issue p. eaal4326

  12. Tropical Forest

    Past human influences on Amazonian forest

    1. Andrew M. Sugden

    The marks of prehistoric human societies on tropical forests can still be detected today. Levis et al. performed a basin-wide comparison of plant distributions, archaeological sites, and environmental data. Plants domesticated by pre-Columbian peoples are much more likely to be dominant in Amazonian forests than other species. Furthermore, forests close to archaeological sites often have a higher abundance and richness of domesticated species. Thus, modern-day Amazonian tree communities across the basin remain largely structured by historical human use.

    Science, this issue p. 925

  13. Organic Chemistry

    Boron choreographs a double reaction

    1. Jake Yeston

    In the widely used Suzuki coupling reaction, boron surrenders an olefinic substituent to a metal catalyst en route to carbon-carbon bond formation. Kischkewitz et al. report a metal-free alternative pathway, wherein the boron stays bound to one end of the olefin while a carbon radical attacks the other end. Charge transfer then prompts migration of an alkyl or aryl group from the boron to form a second carbon-carbon bond. The boron can subsequently be displaced, generating a versatile array of alcohols, lactones, and quaternary carbon centers from simple precursors.

    Science, this issue p. 936

  14. Brain Microcircuits

    Layer-specific interneuron activity

    1. Peter Stern

    Somatostatin-expressing interneurons are an important group of inhibitory neurons in the brain that target and thus control the dendrites of pyramidal cells. These interneurons have recently been shown to play a role in sensorimotor integration, reinforcement encoding, and selective attention. Muñoz et al. used channelrhodopsin-assisted patching to investigate the spatiotemporal pattern of neocortical dendritic inhibition in vivo. They were able to record the activity of somatostatin-expressing interneurons in all neocortical layers in behaving mice. The results provide a framework for understanding the changes in dendritic inhibition that take place in the neocortex during active behaviors. This framework is very distinct from the view obtained from previous recordings that were restricted to interneurons in the superficial layers of the neocortex.

    Science, this issue p. 954

  15. Adaptation

    Climate-driven selection

    1. Sacha Vignieri

    Climate change will fundamentally alter many aspects of the natural world. To understand how species may adapt to this change, we must understand which aspects of the changing climate exert the most powerful selective forces. Siepielski et al. looked at studies of selection across species and regions and found that, across biomes, the strongest sources of selection were precipitation and transpiration changes. Importantly, local and regional climate change explained patterns of selection much more than did global change.

    Science, this issue p. 959

  16. Protein Folding

    Pulling apart protein unfolding

    1. Valda Vinson

    Elucidating the details of how complex proteins fold is a longstanding challenge. Key insights into the unfolding pathways of diverse proteins have come from single-molecule force spectroscopy (SMFS) experiments in which proteins are literally pulled apart. Yu et al. developed a SMFS technique that could unfold individual bacteriorhodopsin molecules in a native lipid bilayer with 1-µs temporal resolution (see the Perspective by Muller and Gaub). The technique delivered a 100-fold improvement over earlier studies of bacteriorhodopsin and revealed many intermediates not seen before. The authors also observed unfolding and refolding transitions between intermediate states.

    Science, this issue p. 945; see also p. 907

  17. Evolution

    How new species evolve

    1. Julia Fahrenkamp-Uppenbrink

    Recent research has highlighted the interplay between environment and genetic changes that leads to speciation. In a Perspective, Grant and Grant discuss evidence from a range of species, including their own decades-long field research on Darwin's finches in the Galapagos archipelago. Together, the research shows how genetic variation can be generated as species diverge. Knowledge of the genetic mechanisms, such as mutations and inversions, introgressive hybridization, and release of cryptic variation, must be complemented by intensive field study to understand the causes and fitness consequences of selection.

    Science, this issue p. 910

  18. Cardiovascular Biology

    Protecting the heart from bad stress

    1. Wei Wong

    An increased workload causes the heart to enlarge. When this occurs in response to high levels of stress, it is pathological and contributes to heart failure. The protein complex mTORC1 promotes cell growth and inhibits autophagy, a form of cellular digestion. Simonson et al. found that in mice, pathological stress, but not physiological stress, increased the levels of the mTORC1 inhibitor DDiT4L. In cardiomyocytes and mice, DDiT4L overexpression was associated with reduced mTORC1 signaling and increased autophagy. Thus, regulation of stress-induced autophagy by DDiT4L may enable the heart to cope with pathological levels of stress.

    Sci. Signal. 10, eaaf5967 (2017).

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