This Week in Science

Science  02 Nov 2018:
Vol. 362, Issue 6414, pp. 554
  1. Physics

    Snapshots of a phase transition

    1. Ian S. Osborne

    Depiction of the insulator-to-metal transition of vanadium dioxide

    CREDIT: GREG STEWART/SLAC NATIONAL ACCELERATOR LABORATORY

    Time-resolved x-ray scattering can be used to investigate the dynamics of materials during the switch from one structural phase to another. So far, methods provide an ensemble average and may miss crucial aspects of the detailed mechanisms at play. Wall et al. used a total-scattering technique to probe the dynamics of the ultrafast insulator-to-metal transition of vanadium dioxide (VO2) (see the Perspective by Cavalleri). Femtosecond x-ray pulses provide access to the time- and momentum-resolved dynamics of the structural transition. Their results show that the photoinduced transition is of the order-disorder type, driven by an ultrafast change in the lattice potential that suddenly unlocks the vanadium atoms and yields large-amplitude uncorrelated motions, rather than occurring through a coherent displacive mechanism.

    Science, this issue p. 572; see also p. 525

  2. Archaeology

    Stress in Neanderthal children

    1. Mark Aldenderfer

    Although environmental variability, such as extreme seasonal cold, is believed to have influenced human evolution, it is difficult to measure its effects directly because of the coarseness of standard analytical methods. Using oxygen-isotope and trace-element analysis on microsamples of tooth enamel from two Neanderthal children from the archaeological site of Payre, France, Smith et al. discovered evidence for extreme wintertime stress in these children, including probable weight loss and exposure to toxic chemicals in the environment, most notably lead. More detailed analyses of one of the children showed that the child was born in the spring and weaned before winter at 2.5 years of age.

    Sci. Adv. 10.1126/sciadv.aau9483 (2018).

  3. Structural Biology

    Nucleosomal DNA transcription

    1. Steve Mao

    In eukaryotes, the basic chromatin unit nucleosome stalls RNA polymerase II (RNAPII) when it transcribes genetic information on DNA. Using cryo–electron microscopy, Kujirai et al. explored seven structures of the RNAPII-nucleosome complex, in which RNAPII pauses at four locations on the nucleosome. These serial snapshots of the RNAPII progression reveal the molecular mechanism of how RNAPII peels the nucleosomal DNA off the histone stepwise.

    Science, this issue p. 595

  4. Neuroscience

    Posture in the brain

    1. Peter Stern

    Our understanding of the neural basis of motor control originates in studies of eye, hand, and arm movements in primates. Mimica et al. investigated neuronal representations of body postures in the posterior parietal and frontal motor cortices with three-dimensional tracking of freely moving rodents (see the Perspective by Chen). Both brain regions represented posture rather than movements and self-motion. Decoding the activity of neurons in the two regions accurately predicted an animal's posture.

    Science, this issue p. 584; see also p. 520

  5. Microbiota

    Gut microbiota selects fungi

    1. Caroline Ash

    Fungi, such as Candida albicans, are found in the mammalian gut, but we know little about what they are doing there. Tso et al. put C. albicans under evolutionary pressure by serial passage in mice that were treated with antibiotics and were thus lacking gut bacteria (see the Perspective by d'Enfert). Passage accelerated fungal mutation, especially around the FLO8 gene, resulting in low-virulence phenotypes unable to form hyphae. Nevertheless, these phenotypes stimulated proinflammatory cytokines and conferred transient cross-protection against several other gut inhabitants. However, if an intact microbiota was present, only the virulent hyphal forms persisted.

    Science, this issue p. 589; see also p. 523

  6. Anti-Flu Therapy

    Durable influenza protection

    1. Seth Thomas Scanlon

    Vaccines are indispensable for the control and prevention of influenza, but there are several challenges to efficacy. Some individuals respond poorly to vaccination, and virus variation makes targeting optimal antigens difficult. Broadly neutralizing antibodies are one solution, but they have their own pitfalls, including limited cross-reactivity to both influenza A and B strains and the need for repeated injections. Now, Laursen et al. have developed multidomain antibodies with breadth and potency. Administered intranasally to mice with an adeno-associated virus vector, the antibodies provided durable and continuous protection from a panoply of influenza strains.

    Science, this issue p. 598

  7. Parkinson's Disease

    The benefits of a missing appendix

    1. Orla M. Smith

    Misfolded α-synuclein is a pathological hallmark of Parkinson's disease (PD). Killinger et al. report that the human appendix contains an abundance of misfolded α-synuclein and that removal of the appendix decreases the risk of developing PD. The appendixes of both individuals with PD and healthy individuals contained abnormally cleaved and aggregated forms of α-synuclein, analogous to those found in postmortem brain tissue from PD patients. Furthermore, α-synuclein derived from the appendix seeds rapid aggregation of recombinant α-synuclein in vitro. In two large-scale epidemiological studies, an appendectomy occurring decades before reduced the risk of developing PD.

    Sci. Transl. Med. 10, eaar5280 (2018).

  8. Nanomaterials

    More alloying on silica

    1. Phil Szuromi

    Controlling the stoichiometry and achieving a high degree of alloying of metals at ultrasmall scales for catalysis can be difficult. Double complex salts, formed by a cation like Pd(NH3)42+ and an anion like IrCl62−, should be excellent precursors but are poorly soluble and difficult to adsorb directly on metal oxide surfaces. Ding et al. show that sequentially adsorbing the cations and anions from organic solvents onto a silica surface, followed by heating in hydrogen, creates well-mixed nanoparticles, most less than 3 nanometers in diameter, for a variety of alloys. These materials were then tested as catalysts for acetylene hydrogenation to ethylene.

    Science, this issue p. 560

  9. Organic Chemistry

    Steps to smaller rings

    1. Jake Yeston

    Certain ring-forming reactions in organic chemistry are efficient because the orbital symmetries match up in the reactants and products. Oxyallyl ions tend to react with dienes in this paradigm to form seven-membered rings. Under palladium catalysis, Trost et al. redirected this reaction toward more common five-membered tetrahydrofuran rings by appending an ester to the diene. Although that pathway is symmetry-forbidden, the electron-withdrawing ester appears to stabilize a key intermediate along a stepwise route to the smaller ring.

    Science, this issue p. 564

  10. Neurodegeneration

    PAR promotes α-synuclein toxicity

    1. Stella M. Hurtley

    How pathologic α-synuclein (α-syn) leads to neurodegeneration in Parkinson's disease (PD) remains poorly understood. Kam et al. studied the α-syn preformed fibril (α-syn PFF) model of sporadic PD (see the Perspective by Brundin and Wyse). They found that pathologic α-syn–activated poly(adenosine 5′-diphosphate–ribose) (PAR) polymerase–1 (PARP-1) and inhibition of PARP or knockout of PARP-1 protected mice from pathology. The generation of PAR by α-syn PFF–induced PARP-1 activation converted α-syn PFF to a strain that was 25-fold more toxic, termed PAR–α-syn PFF. An increase of PAR in the cerebrospinal fluid and evidence of PARP activation in the substantia nigra of PD patients indicates that PARP activation contributes to the pathogenesis of PD through parthanatos and conversion of α-syn to a more toxic strain.

    Science, this issue p. eaat8407; see also p. 521

  11. Drug Discovery

    Thalidomide-targeted degradation

    1. Paula A. Kiberstis

    Thalidomide and its analogs improve the survival of patients with multiple myeloma and other blood cancers. Previous work showed that the drugs bind to the E3 ubiquitin ligase Cereblon, which then targets for degradation two specific zinc finger (ZF) transcription factors with a role in cancer development. Sievers et al. found that more ZF proteins than anticipated are destabilized by thalidomide analogs. A proof-of-concept experiment revealed that chemical modifications of thalidomide can lead to selective degradation of specific ZF proteins. The detailed information provided by structural, biochemical, and computational analyses could guide the development of drugs that target ZF transcription factors implicated in human disease.

    Science, this issue p. eaat0572

  12. Epidemiology

    Predicting hosts and vectors

    1. Caroline Ash

    During outbreaks of mysterious infections, events can rapidly become dangerous and confusing. A combination of increasing experience with outbreaks and genome-sequencing technology now means the pathogen can often be identified within days. But for some of the most frightening viral pathogens, the originating hosts and possible vectors often remain obscure. Babayan et al. took sequence data from more than 500 single-stranded RNA viruses (see the Perspective by Woolhouse) and used machine-learning algorithms to extract evolutionary signals imprinted in the virus sequence that offer information about its original hosts and if an arthropod vector, and what type, plays a part in the virus's natural ecology.

    Science, this issue p. 577; see also p. 524

  13. Metallurgy

    Stronger copper through twin power

    1. Brent Grocholski

    Materials with structural gradients often have unique combinations of properties. Gradient-structured materials are found in nature and can be engineered. Cheng et al. made a structural gradient by introducing gradients of crystallographic twins into copper. This strategy creates bundles of dislocations in the crystal interiors, which makes the metal stronger than any of the individual components. This method offers promise for developing high-performance metals.

    Science, this issue p. eaau1925

  14. Paleoclimatology

    East Asian monsoon mysteries

    1. H. Jesse Smith

    What exactly does the oxygen isotopic composition of speleothems tell us about the East Asian monsoon? They provide magnificent, detailed records of hydroclimate, but precisely what aspects of hydroclimate they record is unclear. Zhang et al. present data from two speleothems from central eastern China for the period from 21,000 to 10,000 years ago and suggest that the cause of the oxygen isotopic variability that they observe is more complex than simple changes in monsoon strength or intensity (see the Perspective by McGee). Alternatively, this variation may reflect the lengths of various phases of the monsoon and the regional heterogeneity of the East Asian hydroclimate.

    Science, this issue p. 580; see also p. 518

  15. Vascular Biology

    RSK2 restricts blood vessel diameter

    1. Wei Wong

    Phosphorylation of myosin proteins enables smooth muscle cells to contract and cause vasoconstriction. This phosphorylation event has generally been attributed to myosin light chain kinase. However, Artamonov et al. discovered that the kinase RSK2 was activated by intraluminal pressure or stimuli that promote vasoconstriction in resistance arteries and that it phosphorylated smooth muscle myosin. Mice lacking RSK2 had dilated arteries and lower blood pressure than wild-type littermates. RSK2 is a possible drug target for manipulating blood pressure.

    Sci. Signal. 11, eaar3924 (2018).

  16. Quantum Optics

    Protecting entangled pairs

    1. Ian S. Osborne

    Photons are readily generated, are fast and can travel vast distances, and are ideal carriers of quantum information. Practical applications, such as quantum computing, will likely be based on an optical-chip platform and require the manipulation of multiphoton states. The inevitable scattering and loss of photons in such a platform would be detrimental for application. Blanco-Redondo et al. show how a specially designed optical circuit based on topology can offer protection for propagating biphoton states. The results show that topological design consideration could provide the desired robustness required for quantum optical circuitry.

    Science, this issue p. 568

  17. Fibrosis

    Type 3 injury

    1. Christiana N. Fogg

    Chronic liver injury caused by infection, toxins, or other inflammatory conditions can lead to liver fibrosis. Fabre et al. define a role for the type 3 cytokines interleukin-17A (IL-17A) and IL-22 in driving transforming growth factor–β (TGF-β)–dependent fibrosis. IL-17A and IL-22 become increased in intrahepatic lymphocytes from patients with hepatitis. Hepatic stellate cells treated with IL-22 showed enhanced p38 mitogen-activated protein kinase–dependent TGF-β signaling. Liver-resident neutrophils and mast cells were identified as the primary sources of IL-17 in humans, and mouse studies showed that blockade of IL-17A and IL-22 could reduce fibrosis.

    Sci. Immunol. 3, eaar7754 (2018).

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