This Week in Science

Science  25 Jul 2014:
Vol. 345, Issue 6195, pp. 413
  1. Dinosaur Evolution

    Feathers, not just for the birds?

    1. Sacha Vignieri

    Artist's view of the new species


    Theropod dinosaurs, thought to be the direct ancestors of birds, sported birdlike feathers. But were they the only feathery dino group? Godefroit et al. describe an early neornithischian dinosaur with both early feathers and scales. This seemingly feathery nontheropod dinosaur shows that feathers were not unique to the ancestors of birds and may even have been quite widespread.

    Science, this issue p. 451

  2. RNA Function

    Problems making proteins kills nerve cells

    1. Guy Riddihough

    Neurodegeneration is associated with a variety of different diseases, but its cellular roots are often obscure. Ishimura et al. find that mutant mice whose brain cells start to die rapidly soon after birth have lost the function of two vital cellular components (see the Perspective by Darnell). The first is a protein that releases stalled ribosomes stuck on messenger RNA (mRNA); the second is a transfer RNA (tRNA), which reads the code for arginine in the mRNA. This tRNA is expressed predominantly in the central nervous system. The lack of the tRNA leads to increased ribosomal stalling at arginine codons, which, when left uncorrected, blocks protein synthesis and proves fatal.

    Science, this issue p. 455; see also p. 378

  3. Cystic Fibrosis

    In CF, two drugs are no better than one

    1. Yevgeniya Nusinovich

    Cystic fibrosis (CF), a disabling lung disease, is caused by mutations in a protein called CFTR, which acts as a channel to move chloride ions into and out of cells. Ivacaftor, the only targeted drug available, does not work well for the severest, most common form of disease. Cholon et al. and Veit et al. now explain why efforts to improve CF treatment by combining ivacaftor with new drugs have failed. Ivacaftor increases mutant CFTR's activity, but it only works when CFTR is on the cell surface. The new drugs under development bring mutant CFTR to the surface, but combining the two types of drugs has not been effective because ivacaftor also makes CFTR less stable, so cells remove it quickly from their membranes.

    Sci. Transl. Med. 6, 246ra96, 246ra97 (2014).

  4. Metamaterials

    To cast no shadow in a murky medium

    1. Ian S. Osborne

    Cloaks can hide objects from view, but what about their shadows? Schittny et al. devised a cloak to remove even the shadow of an object embedded in a murky medium in front of a computer screen (see the Perspective by Smith). They engineered a core-shell structure within which an object could be hidden and tailored the optical properties of the cloak to match that of the medium. Light was routed around the cloak, leaving no trace of the hidden object.

    Science, this issue p. 427; see also p. 384

  5. Cell Biology

    Changing skin cells in development with TGF-β

    1. Jason D. Berndt

    Transforming growth factor–β (TGF-β) makes some cells stop dividing, separate from one another, and start migrating. This process, called the epithelial-to-mesenchymal transition, occurs during normal development and can help cancers progress. D'Souza et al. cultured skin cells and measured changes in their proteins as they underwent this process. TGF-β caused thousands of protein changes that varied depending on how long cells were exposed to TGF-β. The protein changes correlated with changes in cell behavior. The authors modeled the network of interacting proteins affected by TGF-β, creating a road map that can explain how TGF-β influences cell behavior.

    Sci. Signal. 7, rs5 (2014).

  6. Quantum Metrology

    Subtle entanglement in an atomic cloud

    1. Jelena Stajic

    In the quantum world, atoms can be correlated with each other—“entangled”—which reduces the uncertainty in the knowledge of some of their properties. Physicists then use this reduced uncertainty to perform precision measurements. Strobel et al. made an unusual type of entangled state consisting of hundreds of ultracold Rb atoms. These methods may in the future be able to generate states that will be more useful in precision measurement.

    Science, this issue p. 424

  7. Exoplanet Detection

    Tricky star plays sleight-of-light

    1. Margaret M. Moerchen

    Planetary system in Gliese 581


    Two signatures in starlight thought to be written by extrasolar planets may turn out to be forgeries. Astronomers often attribute periodic shifts in a star's apparent motion toward and away from us to the tug of orbiting planets. Robertson et al. studied archival spectra of the star Gliese 581 to assess another potential cause: magnetic activity on the star's surface. The signals once attributed to two planet candidates instead resulted from the combined effect of starspots and stellar rotation. Planet hunters be warned—correct for stellar activity in your data analyses.

    Science, this issue p. 440

  8. Induced Earthquakes

    Wastewater disposal linked to earthquakes

    1. Nicholas S. Wigginton

    The number of earthquakes is increasing in regions with active unconventional oil and gas wells, where water pumped at high pressure breaks open rock containing natural gas, leaving behind wastewater in need of disposing. Keranen et al. show that the steep rise in earthquakes in Oklahoma, USA, is likely caused by fluid migration from wastewater disposal wells. Twenty percent of the earthquakes in the central United States could be attributed to just four of the wells. Injected fluids in high-volume wells triggered earthquakes over 30 km away.

    Science, this issue p. 448

  9. Clathrin Adaptors

    A membrane-activated switch to bind clathrin

    1. Stella M. Hurtley

    Clathrin-mediated endocytosis—the process by which cells take up nutrients and signals within clathrin-coated vesicles—is very well understood. Kelly et al. reveal an unanticipated layer of regulation in this process. The proteins AP2 and clathrin are the major constituents of endocytic clathrin-coated vesicles. AP2 and clathrin stick together through a clathrin-binding motif in AP2. The authors now show that AP2's clathrin-binding motif is normally buried within the core of the AP2 protein. AP2 only ejects its clathrin-binding motif and recruits clathrin if it is associated with the correct cell membrane and an endocytic cargo.

    Science, this issue p. 459

  10. Ecological Networks

    A structural approach to species interactions

    1. Andrew M. Sugden

    What determines the stability of ecological networks? Rohr et al. devised a conceptual approach to study interactions between species that emphasizes the role of network structure (see the Perspective by Pawar). Using the example of mutualistic networks of communities of plants and their pollinator species, they show how the structure of networks can determine the persistence of the interactions. Network structures and architectures observed in nature intrinsically match the most stable solution. This approach has promise for application to questions of ecological community stability under global change.

    Science, this issue 10.1126/science.1253497; see also p. 383

  11. Dual Catalysis

    A bright outlook for carbon coupling

    1. Jake Yeston

    In contemporary organic chemistry, it is straightforward to forge bonds between unsaturated carbons (i.e., carbons already engaged in double bonds) using cross-coupling catalysis. The protocol runs into some trouble, however, if one or both starting carbon centers are saturated (purely single-bonded). Tellis et al. and Zuo et al. independently found that combining a second, light-activated catalyst with a nickel cross-coupling catalyst could achieve selective coupling of saturated and unsaturated reagents (see the Perspective by Lloyd-Jones and Ball). Their methods rely on single-electron transfer from the light-activated catalyst to the saturated carbon, thereby enhancing its reactivity more effectively than the two-electron mechanisms prevailing in traditional protocols.

    Science, this issue p. 433, p. 437; see also p. 381

  12. Quantum Computing

    How to benchmark a quantum computer

    1. Ian S. Osborne

    Quantum machines offer the possibility of performing certain computations much faster than their classical counterparts. However, how to define and measure quantum speedup is a topic of debate. Rønnow et al. describe methods for fairly evaluating the difference in computational power between classical and quantum processors. They define various types of quantum speedup and consider quantum processors that are designed to solve a specific class of problems.

    Science, this issue p. 420

  13. Ultrafast Optics

    Toward the control of light with light

    1. Ian S. Osborne

    Optic fibers form the backbone of the communications sector and carry huge amounts of data around the globe. Nissim et al. show that small perturbations within the core of a fiber give rise to interactions between photons. The strength of the interaction could be controlled by carefully characterizing and splicing together different lengths of fiber. The interactions between the photons were enhanced so that a strong signal beam could be switched off with just a few photons.

    Science, this issue p. 417

  14. Quantum Simulation

    Characterization of a quantum simulator

    1. Jelena Stajic

    Ultracold gases can be used to simulate the behavior of more complicated systems, such as solid materials. Senko et al. developed a method similar to nuclear magnetic resonance that can be used to validate the properties of such simulators. They demonstrated the method on an array of interacting trapped ions that simulate magnetism. A modulated magnetic field resonantly enhanced the transfer of the population between the different configurations of the system. The authors varied the modulation frequency to measure the energy of each configuration and mapped the effective interactions.

    Science, this issue p. 430

  15. Paleoclimate

    Climates conspire together to make big changes

    1. H. Jesse Smith

    The regional climates of the North Pacific and North Atlantic fluttered between synchrony and asynchrony during the last deglaciation, with correspondingly more and less intense effects on the rest of the world, researchers have found. The climate system can be highly nonlinear, meaning that small changes in one part can lead to much larger changes elsewhere. This type of behavior is especially evident during transitions from glacial to interglacial conditions, when climate is affected by a wide variety of time-varying influences and is relatively unstable. Praetorius and Mix present a record of North Pacific climate over the past 18,000 years. When the climates of the more local high-latitude Pacific and Atlantic sectors varied in parallel, large, abrupt climate fluctuations occurred on a more global scale.

    Science, this issue p. 444

  16. Actin Cytoskeleton

    Making tropomodulin find the right point

    1. Stella M. Hurtley

    Actin filaments are a key component of the cell's cytoskeleton. Actin filaments have a characteristic polarized architecture with a so-called barbed end and a pointed end—so described because of how the filaments look under the electron microscope when they are coated with tropomyosin. Rao et al. describe crystal structures of a protein that uniquely binds and caps the pointed end of actin filaments. This protein, tropomodulin, binds to several actin subunits and to a couple of tropomyosin molecules, which generates a high-affinity specific cap to the filaments by combining low-affinity interactions.

    Science, this issue p. 463