This Week in Science

Science  01 Jan 2016:
Vol. 351, Issue 6268, pp. 37
  1. THREE-DIMENSIONAL PRINTING

    Printing ceramics into complex shapes

    1. Marc S. Lavine

    Polymer-derived ceramic lattices exhibit high thermal shock resistance and low thermal conductivity

    PHOTO: 2015 HRL LABORATORIES - PHOTO BY DAN LITTLE PHOTOGRAPHY

    Some materials, such as thermoplastics and metals, are naturally suited to being 3D printed because the individual particles can be fused together by applying heat. In contrast, ceramics do not fuse together the same way. Eckel et al. developed a way to pattern specific preceramic monomers using either 3D printing or stereolithography into complex, curved, and porous shapes. Upon heating, they observed almost no shrinkage, and the formed parts showed exceptional thermal stability.

    Science, this issue p. 58

  2. VIROLOGY

    Coronaviruses in the Middle East

    1. Caroline Ash

    Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe acute respiratory illness and kills about a third of people infected. The virus is common in dromedary camels, which can be a source of human infections. In a survey for MERSCoV in over 1300 Saudi Arabian camels, Sabir et al. found that dromedaries share three coronavirus species with humans. Diverse MERS lineages in camels have caused human infections, which suggests that transfer among host species occurs quite easily. Haagmans et al. made a MERS-CoV vaccine for use in camels, using poxvirus as a vehicle. The vaccine significantly reduced virus excretion, which should help reduce the potential for transmission to humans, and conferred cross-immunity to camelpox infections.

    Science, this issue p. 81, p. 77

  3. GENOME EDITING

    Making the correct cut

    1. Valda Vinson

    The CRISPR/Cas system is a prokaryotic immune system that targets and cuts out foreign DNA in bacteria. It has been adopted for gene editing because it can be designed to recognize and cut specific locations in the genome. A challenge in developing clinical applications is the potential for off-target effects that could result in DNA cleavage at the wrong locations. Slaymaker et al. used structure-guided engineering to improve the specificity of Streptococcus pyogenes Cas9 (SpCas9). They identified enhanced-specificity variants (eSpCas9) that display reduced off-target cleavage while maintaining robust on-target activity

    Science, this issue p. 84

  4. PROTEIN TRANSLOCATION

    Seeing the signal sequence in action

    1. Stella M. Hurtley

    Protein translocation across the endoplasmic reticulum (ER) involves the interaction of a signal sequence with the protein translocation channel. Although much work has looked at the details of protein translocation, questions remain. Voorhees and Hegde present a single-particle cryoelectron microscopy study of the mammalian ER translocation apparatus at the point in which the signal sequence is engaging the translocation pore.

    Science, this issue p. 88

  5. ORGANIC CHEMISTRY

    A two-for-one twist on Suzuki coupling

    1. Jake Yeston

    The Suzuki-Miyaura coupling reaction is one of the most widely used ways of making carbon-carbon bonds. Essentially a palladium catalyst activates one carbon fragment and then links it to a second fragment pulled from boron. Zhang et al. now demonstrate a twist on the conventional pathway (see the Perspective by Fyfe and Watson). In their system, the palladium initially coaxes together two carbon fragments on one boron center. Then the catalyst stitches a second C-C bond to a third, external fragment. A chiral ligand renders the reaction highly enantio-selective.

    Science, this issue p. 70; see also p. 26

  6. PHOTOVOLTAICS

    Efficient luminescent solar cells

    1. Zakya H. Kafafi

    Shine on! Bi et al. fabricated a perovskite-based solar cell that can create extraordinarily high solar-to-electric power conversion and intense electroluminescence. The new-fangled cells should help to produce solar technologies that approach the upper limit for open-circuit voltage. These devices are likely to be competitive with “state-of-the-art” conventional solar technologies and may be used in tandem with more traditional solar cells.

    Sci. Adv. 10.1126.sciadv.01170 (2016).

  7. CARDIOLOGY

    Disruptive technology

    1. Megan Frisk

    Healthy hearts beat synchronously; failing hearts often lose this coordination. Normally, pacemakers are used to reset the heart's rhythm. Kirk et al. used pacemakers to restore synchrony by inducing periods of abnormal rhythm—called pacemaker-induced transient asynchrony (PITA). In dogs with heart failure, PITA halted heart chamber dilation and negative remodeling of heart tissue. It also improved cell signaling and force generation, and supported normal muscle fiber structure and function. Some people with pacemakers do not respond to standard resynchronization protocols; PITA could offer them the possibility of restoring rhythm.

    Sci. Transl. Med. 7, 319ra207 (2015).

  8. BLACK HOLE PHYSICS

    Transient radio jet from a black hole

    1. Keith T. Smith

    When a star passes too close to a supermassive black hole, it gets ripped apart by the gravitational forces. This causes a tidal disruption flare as the material falls into the black hole. van Velzen et al. monitored one such flare with radio telescopes and found evidence for a transient relativistic jet launched by the black hole (see the Perspective by Bower). Larger jets are a feature of active galactic nuclei and have a profound effect on their host galaxy, but are poorly understood. The results will aid our understanding of how black holes “feed” and of the processes governing jet formation.

    Science, this issue p. 62; see also p. 30

  9. MICROBIAL ENGINEERING

    Using light in the darkness

    1. Nicholas S. Wigginton

    Solid-state devices can efficiently capture solar energy to produce chemicals and fuels from carbon dioxide. Yet biology has already developed a high-specificity, low-cost system to do just that through photosynthesis. Sakimoto et al. developed a biological-inorganic hybrid that combines the best of both worlds (see the Perspective by Müller). They precipitated semiconductor nanoparticles on the surface of a nonphotosynthetic bacterium to serve as a light harvester. The captured energy sustained cellular metabolism, producing acetic acid: a natural waste product of respiration.

    Science, this issue p. 74; see also p. 34

  10. ANTIBIOTIC RESISTANCE

    Evolving antibiotic rescue stratagems

    1. Caroline Ash

    Antibiotic resistance threatens to put modern medicine into reverse. But we are not at the end of our options for currently available drugs. Baym et al. review what can be done by using combinations of antibiotics to circumvent bacteria's evolutionary strategies. For instance, resistance to one drug may cause sensitivity to another, the effectiveness of two drugs can be synergized by a resistance mutation, and some negative drug interactions may even be beneficial in selecting against resistance. Although not simple to assess, drug combinations still have something to offer for the development of sorely needed anti-infectives.

    Science, this issue p. aad3292

  11. NEURAL CIRCUITS

    A way to modulate reward-seeking

    1. Peter Stern

    Which brain regions are causally involved in reward-related behavior? Ferenczi et al. combined focal, cell type-specific, optogenetic manipulations with brain imaging, behavioral testing, and in vivo electrophysiology (see the Perspective by Robbins). Stimulation of midbrain dopamine neurons increased activity in a brain region called the striatum and was correlated with reward-seeking across individual animals. However, elevated excitability of an area called the medial prefrontal cortex reduced both striatal responses to the stimulation of dopamine neurons and the behavioral drive to seek the stimulation of dopamine neurons. Finally, modulating the excitability of medial prefrontal cortex pyramidal neurons drove changes in neural circuit synchrony, as well as corresponding anhedonic behavior. These observations resemble imaging and clinical phenotypes observed in human depression, addiction, and schizophrenia.

    Science, this issue p. aac9698; see also p. 24

  12. BEHAVIORAL GENETICS

    Epigenetic control of caste-specific foraging

    1. Laura M. Zahn

    In carpenter ants, separate behavioral classes, known as castes, are determined by the epigenetic regulation of genes. Simola et al. treated ants of different castes with drugs that affected histone acetylation. Reducing histone acetylation stimulated scouting and foraging behavior. The foraging and scouting behaviors of young ants were permanently changed by directly injecting their brains with histone acetylation inhibitors.

    Science, this issue p. aac6633

  13. METABOLISM

    From sensing leucine to metabolic control

    1. L. Bryan Ray

    The mTORC1 protein kinase complex plays central roles in regulating cell growth and metabolism and is implicated in common human diseases such as diabetes and cancer. The level of the amino acid leucine tells an organism a lot about its physiological state, including how much food is available, how much insulin is going to be needed, and whether new muscle mass can be made (see the Perspective by Buel and Blenis). Wolfson et al. identified a biochemical sensor of leucine, Sestrin2, which connects the concentration of leucine to the control of organismal metabolism and growth. When leucine bound to Sestrin2, it was released from a complex with the mTORC1 regulatory factor GATOR2, activating the mTORC1 complex. Saxton et al. describe the crystal structure of Sestrin2 and show how it specifically detects leucine. Aylett et al. determined the structure of human mTORC1 by cryoelectron microscopy and the crystal structure of a regulatory subunit, Raptor. The results reveal the structural basis for the function and intricate regulation of this important enzyme, which is also a strategic drug target.

    Science, this issue p. 43, p. 48, p. 53; see also p. 25

  14. ASTROCHEMISTRY

    Water isomers hide their origin

    1. Keith T. Smith

    H2O exists in two spin isomers, ortho and para, in a ratio of 3:1 at room temperature. Some astronomical observations have found water with a ratio of less than 3, thought to be due to water being photodesorbed from ice that had been formed at very low temperatures (≾30 K). Hama et al. tested this idea in the laboratory, by forming water ice at low temperature and then photodesorbing it to measure the ortho:para ratio. They found a ratio of 3, even at 10 K. Thus, another explanation for the low ratios in some astronomical objects must be found.

    Science, this issue p. 65

  15. MEMBRANES

    Separating H+ from D+

    1. Marc S. Lavine

    In many respects, hydrogen and deuterium show similar properties because they share the same number of protons and electrons and only differ by one neutron. However, when you strip away the electron, a proton ends up having less than half the radius of a deuterion. Lozada-Hidalgo et al. used two-dimensional membranes of graphene or hexagonal boron nitride to separate these two charged isotopes, with a separation factor of about 10.

    Science, this issue p. 68

  16. COMPUTER SCIENCE

    Computing power of crowds

    1. Julia Fahrenkamp-Uppenbrink

    Every time a person transcribes distorted text to prove that they are human and gain access to a web page, they contribute to a massive effort to digitize books and newspapers. This is just one of many human computation systems that take advantage of the strengths of both humans and computers. In a Perspective, Michelucci and Dickinson chart recent progress in developing sophisticated human computation systems that can address complex economic, medical, and environmental problems. Human visual perception remains unmatched by machines, but humans are less predictable. Human computation developers must therefore take account of research into human cognition and decision-making.

    Science, this issue p. 32

  17. CANCER

    Pathway activity as a biomarker

    1. Nancy R. Gough

    Understanding signaling networks may enable the prediction of disease prognosis. Fey et al. constructed a computational model that reproduces the all-or-nothing, switch-like activation of the kinase JNK in neuroblastoma (see also the Focus by Kim and Schoeberl). Switch-like activation of JNK leads to cell death. The authors integrated patient data about the levels of JNK pathway components in neuroblastoma samples into the model, to simulate the activity of the pathway and accurately predict survival based on the dynamic properties of the pathway. Alterations in the network that prevented the switch-like activation of JNK were associated with poor survival of neuroblastoma patients.

    Sci. Signal. 8, ra130 and fs21 (2015).

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