This Week in Science

Science  01 Dec 2017:
Vol. 358, Issue 6367, pp. 1143
  1. Biological Optics

    Fine-tuned for image formation

    1. Marc S. Lavine

    Scallops have multiple reflective eyes (blue) in their mantle.

    CREDIT: DAVID LIITTSCHWAGER/NATIONAL GEOGRAPHIC CREATIVE

    We typically think of eyes as having one or more lenses for focusing incoming light onto a surface such as our retina. However, light can also be focused using arrays of mirrors, as is commonly done in telescopes. A biological example of this is the scallop, which can have up to 200 reflecting eyes that focus light onto two retinas. Palmer et al. find that spatial vision in the scallop is achieved through precise control of the size, shape, and packing density of the tiles of guanine that together make up an image-forming mirror at the back of each of the eyes.

    Science, this issue p. 1172

  2. Solar Cells

    Minimizing losses at interfaces

    1. Phil Szuromi

    Among the issues facing the practical use of hybrid organohalide lead perovskite solar cells is the loss of charge carriers at interfaces. Hou et al. show that tantalum-doped tungsten oxide forms almost ohmic contacts with inexpensive conjugated polymer multilayers to create a hole-transporting material with a small interface barrier. This approach eliminates the use of ionic dopants that compromise device stability. Solar cells made with these contacts achieved maximum efficiencies of 21.2% and operated stably for more than 1000 hours.

    Science, this issue p. 1192

  3. Physics

    Numerics converging on stripes

    1. Jelena Stajic

    The Hubbard model (HM) describes the behavior of interacting particles on a lattice where the particles can hop from one lattice site to the next. Although it appears simple, solving the HM when the interactions are repulsive, the particles are fermions, and the temperature is low—all of which applies in the case of correlated electron systems—is computationally challenging. Two groups have tackled this important problem. Huang et al. studied a three-band version of the HM at finite temperature, whereas Zheng et al. used five complementary numerical methods that kept each other in check to discern the ground state of the HM. Both groups found evidence for stripes, or one-dimensional charge and/or spin density modulations.

    Science, this issue p. 1161, p. 1155

  4. Geophysics

    Gravity gets into the earthquake game

    1. Brent Grocholski

    Earthquakes generate large movements of mass, which slightly change the gravitational field. Unlike the elastic waves that propagate from the earthquake, the gravity perturbations travel at the speed of light. Vallée et al. have finally observed these gravity perturbations in seismometer records from the great Tohoku earthquake in Japan in 2011. The signal would have allowed an accurate magnitude estimation in minutes, rather than hours, for this catastrophic earthquake.

    Science, this issue p. 1164

  5. Paleontology

    Even more like birds

    1. Sacha Vignieri

    Ecological convergence between pterosaurs and birds is often invoked, but to what degree the two groups share behavior is debated. Wang et al. describe a site with more than 100 fossilized pterosaur eggs that reveals that hatchling pterosaurs were likely not as precocial as previously thought (see the Perspective by Deeming). Furthermore, the overlaying of multiple clutches suggests that the pterosaurs may have exhibited breeding site fidelity, similar to rookery-breeding seabirds. Thus, the similarity between these two groups goes beyond wings.

    Science, this issue p. 1197; see also p. 1124

  6. Immunology

    Blood DNases hack the NET

    1. Seth Thomas Scanlon

    Neutrophil extracellular traps (NETs) are lattices of processed chromatin decorated with select secreted and cytoplasmic proteins that trap and neutralize microbes. However, their inappropriate release may do more harm than good by promoting inflammation and thrombosis. Jiménez-Alcázar et al. report that two deoxyribonucleases (DNases), DNASE1 and DNASE1L3, have partially redundant roles in degrading NETs in the circulation (see the Perspective by Gunzer). Knockout mice lacking these enzymes were unable to tolerate chronic neutrophilia, quickly dying after blood vessels were occluded by NET clots. Furthermore, the damage unleashed by clots during septicemia was enhanced when these DNases were absent.

    Science, this issue p. 1202; see also p. 1126

  7. Materials Science

    3D printing with living inks

    1. Lynden Archer

    Multimaterial 3D printing allows spatial segregation of two bacterial strains.

    PHOTOS: SCHAFFNER ET AL., SCI. ADV. 10.1126/SCIADV.AAO6804 (2017)

    Intricate three-dimensional (3D)-printed structures teaming with bacterial life have been created using biocompatible hydrogel inks. Schaffner et al. blended the naturally occurring polymers κ-carrageenan, hyaluronic acid, and fumed silica in nearly equal parts in a salty, bacteria-rich broth. This yielded a nontoxic, functional living ink that could support free-standing objects written in submillimeter-scale printed filaments. Potential applications of such living materials range from degrading pollutants to producing synthetic skin scaffolds.

    Sci. Adv. 10.1126/sciadv.aao6804 (2017).

  8. Structural Biology

    Holding a master regulator in check

    1. Valda Vinson

    A family of eukaryotic protein kinases, the phosphatidylinositol 3-kinase-related kinases (PIKKs), has key functions in DNA repair and nutrient sensing. In humans, ATR kinase locates DNA damage through its partner, ATRIP. Once activated, ATR initiates a cell-cycle cascade that culminates in cell-cycle arrest. Wang et al. determined the high-resolution structure of Mec1-Ddc2 (the yeast homolog of ATR-ATRIP) by electron microscopy. The structure shows the detailed architecture of the multidomain complex that overall forms a dimer of heterodimers. The detailed analysis of the structure reveals how an allosteric mechanism may activate the kinase.

    Science, this issue p. 1206

  9. Muscular Dystrophy

    Making the cut

    1. Orla M. Smith

    Mutations in the dystrophin gene cause Duchenne muscular dystrophy (DMD), a fatal childhood muscle disease. Amoasii et al. sought to optimize the correction of DMD mutations by CRISPR-Cas9 gene editing. They first generated mice in which exon 50, a common mutational hotspot region of the dystrophin gene in humans, was deleted. They then made a single cut in the dystrophin gene with CRISPR-Cas9, which resulted in up to 90% restoration of dystrophin expression in mouse skeletal and heart muscle.

    Sci. Transl. Med. 9, eaan8081 (2017).

  10. Drug Development

    An atlas for drug interactions

    1. Priscilla N. Kelly

    Kinase inhibitors are an important class of drugs that block certain enzymes involved in diseases such as cancer and inflammatory disorders. There are hundreds of kinases within the human body, so knowing the kinase “target” of each drug is essential for developing successful treatment strategies. Sometimes clinical trials can fail because drugs bind more than one target. Yet sometimes off-target effects can be beneficial, and drugs can be repurposed for treatment of additional diseases. Klaeger et al. performed a comprehensive analysis of 243 kinase inhibitors that are either approved for use or in clinical trials. They provide an open-access resource of target summaries that could help researchers develop better drugs, understand how existing drugs work, and design more effective clinical trials.

    Science, this issue p. eaan4368

  11. Cancer

    A bona fide portrayal of tumor growth

    1. Paula A. Kiberstis

    Bone has a well-established role in advanced cancer. It provides a supportive microenvironment for the growth of metastatic cells that escape the primary tumor, which ultimately leads to loss of bone mass. Engblom et al. show that bone may also contribute to early-stage tumorigenesis through a mechanism that leads to an increase in bone mass (see the Perspective by Zhang and Lyden). In mouse models of lung adenocarcinoma, primary tumor cells remotely activated bone-resident cells called osteoblasts, which have a bone-building function. The activated osteoblasts in turn triggered production of a certain type of neutrophil that infiltrates the primary tumor and promotes its growth. Patients with early-stage lung cancer were also found to have an increase in bone density, consistent with the findings in mice.

    Science, this issue p. eaal5081; see also p. 1127

  12. Planar Optics

    Looking sharp with metalenses

    1. Ian S. Osborne

    High-end imaging lenses have tended to be based on bulk optical components. Advances in fabrication techniques have enabled the development of ultrathin, lightweight, and planar lenses (metalenses) that have unprecedented functionalities. These metalenses have the potential to replace or complement their conventional bulk counterparts. Khorasaninejad and Capasso review the evolution of metalenses, summarizing achievements and applications and identifying future challenges and opportunities. Metalenses can have numerous applications, ranging from cellphone camera modules, to wearable displays for augmented and virtual reality and machine vision, to bio-imaging and endoscopy.

    Science, this issue p. eaam8100

  13. Marine Microbiome

    Functional ocean biogeography

    1. Caroline Ash

    Marine ecosystems are well represented in metagenomic and transcriptomic data. These data are not routinely used to test ecosystem models that explore ocean biogeography or biogeochemistry. Coles et al. built a model in which genes for a range of functions were assigned to different suites of simulated microbes (see the Perspective by Rynearson). Communities emerged from the model with realistic biogeographical and biogeochemical profiles when compared to microbial data collected from the Amazon River plume. However, functional composition trumped the details of taxonomy, and different, coevolving community compositions emerged that provided similar biogeochemical outcomes.

    Science, this issue p. 1149; see also p. 1129

  14. Organometallics

    Calcium can breach benzene's defenses

    1. Jake Yeston

    Calcium plays a major, multifaceted role in biology and mineralogy. In organic chemistry, though, it is largely overlooked and overshadowed by the carbon compounds of its cousins lithium and magnesium. Wilson et al. now report that the element was just biding its time: Several organocalcium compounds that they prepared can alkylate benzene by displacing a hydride, with no need for a more conventionally reactive leaving group such as chloride (see the Perspective by Mulvey). This surprising, previously elusive reaction attests to the unusual nucleophilicity of the carbons bound to calcium.

    Science, this issue p. 1168; see also p. 1132

  15. Organic Chemistry

    Lighting the way to drug labeling

    1. Jake Yeston

    It is important during drug development to study how candidate compounds get absorbed and broken down biologically. One common technique for tracking a drug's fate is to label its molecular framework with heavier isotopes of hydrogen (either deuterium or tritium). Loh et al. developed a light-promoted protocol to install these labels on alkyl carbons adjacent to nitrogen. The technique relies on incorporation of the heavy isotope into a thiol from a convenient heavy water source through acid-base chemistry. Next, a photoredox catalyst strips a hydrogen atom equivalent from the carbon, and the thiol engages in radical chemistry to transfer the deuterium or tritium in its place.

    Science, this issue p. 1182

  16. Quantum Simulation

    Putting photons to work

    1. Jelena Stajic

    Interacting quantum particles can behave in peculiar ways. To understand that behavior, physicists have turned to quantum simulation, in which a tunable and clean system can be monitored as it evolves under the influence of interactions. Roushan et al. used a chain of nine superconducting qubits to create effective interactions between normally noninteracting photons and directly measured the energy levels of their system. The interplay of interactions and disorder gave rise to a transition to a localized state. With an increase in the number of qubits, the technique should be able to tackle problems that are inaccessible to classical computers.

    Science, this issue p. 1175

  17. Nanophotonics

    A plasmonic route for mixing waves

    1. Ian S. Osborne

    Nonlinear optics typically requires photons to interact over distances spanning hundreds or thousands of wavelengths. Nonlinear optical devices therefore tend to be bulk components. Nielsen et al. used a polymer material with a high nonlinear coefficient that they embedded within a plasmonic cavity to show that the interaction length scale could be reduced dramatically. The plasmonic cavity focused the light down to the nanoscale, providing an intense electromagnetic field that induced the nonlinear process of four-wave mixing in the polymer. The technique provides a versatile platform for compact nonlinear optical devices.

    Science, this issue p. 1179

  18. Electrocatalysis

    Going with the grain boundaries

    1. Phil Szuromi

    Bulk defects in a metal, such as grain boundaries, can create regions of increased strain at its surface that could affect its catalytic activity. Mariano et al. studied the electroreduction of CO2 to CO on polycrystalline gold films, a reaction that competes with H2 evolution. By annealing the films to create larger grains, they could change the types and distribution of grain boundaries at the surface. Scanning electrochemical cell microscopy revealed that the dislocation density correlated with CO2 electroreduction activity, but such defects had no effect on H2 evolution.

    Science, this issue p. 1187

  19. Ion Channels

    Channeling Ca2+ for cancer

    1. Wei Wong

    Ca2+ influx mediated by the channel Orai1 stimulates transcription factors such as NFAT. Frischauf et al. characterized various cancer-associated Orai1 mutants (see the Focus by Muallem). These constitutively active mutants activated NFAT and also stimulated mitophagy and autophagy, processes that can contribute to tumor progression. The authors determined in detail how Orai1 is gated and how constitutively activating mutations result in increased Ca2+ influx. These findings have implications for Orai1-mediated Ca2+ signaling in diverse cell types.

    Sci. Signal. 10, eaao0358, eaaq0618 (2017).

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