Editors' Choice

Science  01 Jun 2018:
Vol. 360, Issue 6392, pp. 977
  1. Organic Synthesis

    Acetylene in, PAHs out

    1. Phil Szuromi

    Electron density map of polycyclic aromatic hydrocarbons inside a zeolite cage

    CREDIT: S. H. KO ET AL., J. AM. CHEM. SOC. 10.1021/JACS.8B00900 (2018)

    Polyaromatic hydrocarbons (PAHs) are attractive for optoelectronics applications, but their synthesis can be challenging. Solution routes tend to have low yields, and high-temperature vacuum pyrolysis (∼1000°C) generates numerous carbonaceous side products. Ko et al. synthesized PAHs by polymerizing acetylene in Ca2+ ion–exchanged Linde type-A zeolites at ∼400°C. The Ca2+ ions appear to lower the barrier for carbon-carbon bond formation. The PAHs remained trapped in the α-cages of the zeolite but were recovered after dissolving the zeolite with acid. The product mixture exhibited white fluorescence in N-methylpyrrolidone solution. Column chromatography separation isolated violet, blue, green, and orange emitters, with coronene being the main component of the blue emitter.

    J. Am. Chem. Soc. 10.1021/jacs.8b00900 (2018).

  2. Neurodegeneration

    Keeping stress granules in check

    1. Stella M. Hurtley

    Stress granules are membraneless organelles composed of RNAs and proteins that can accumulate in the presence of potentially pathogenic proteins. These include proteins linked to neurodegenerative disorders such as C9-ALS/FTD (amyotrophic lateral sclerosis and frontotemporal dementia linked to C9ORF72). The pathomechanisms of these same disorders can involve disruption of nucleocytoplasmic transport. Zhang et al. found that a variety of components of the nuclear import machinery were sequestered in stress granules, which reduced nucleocytoplasmic transport. Inhibiting stress granule assembly suppressed these transport defects in cells, and it also interfered with the neurodegeneration process in patient-derived iPS (induced pluripotent stem cell–derived) motor neurons and in a fly C9-ALS disease model system.

    Cell 173, 958 (2018).

  3. Vertebrate Paleontology

    Island life

    1. Sacha Vignieri

    A Cretaceous mammal shows signs of island-related adaptation.

    PHOTO: ROB CRANDALL/ALAMY STOCK PHOTO

    Among modern faunas, a well-established phenomenon occurs as species evolve to live on islands. Specifically, many species undergo dwarfism and other related changes after island colonization, likely owing to resource limitation and restriction of landscapes. Csiki-Sava et al. describe a multituberculate mammal from a Cretaceous island in Romania that displays several unusual traits, notably a reduced brain size and domed skull. The authors argue that these changes reflect adaptation to the island habitat of this group and, further, that a small brain (relative to body size) may be a previously undescribed adaptation to insular living.

    Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1801143115 (2018).

  4. Host Defense

    Bacteria restricted via C3-mediated autophagy

    1. Seth Thomas Scanlon

    The complement system has several important host-defense functions. Complement component C3, for example, can enhance phagocytosis, contribute to the bactericidal membrane attack complex, and initiate adaptive immune responses against invading microorganisms. Sorbara et al. uncovered another mechanism by which C3 can control pathogens. They observed interactions between the autophagy protein ATG16L1 and C3. In opsonized intracellular bacteria such as Listeria, this resulted in increased targeting to the autophagy system (xenophagy) and, in turn, greater autophagy-dependent growth restriction. Certain intracellular bacteria, such as Shigella and Salmonella, were able to escape C3-mediated targeting via the omptin proteases IcsP and PgtE, which cleave complement components including C3. Mouse models reveal that C3-mediated autophagy-dependent restriction may be important in protecting host mucosal tissues during the early stages of Listeria infection.

    Cell Host Microbe 23, 644 (2018).

  5. Polymer Colloids

    Structured in a flash

    1. Marc S. Lavine

    Block copolymers will assemble into a range of complex structures driven both by thermodynamics, as defined by the chemical makeup of the blocks, and by the kinetics of the chain motion. When formed into sheets, these structures can range from those with regular periodicity to those with complex, tortuous, random interconnected phases. Grundy et al. developed a scalable process in which a feed stream containing polymers in a solvent contacts a counterstream based on a poor solvent for the polymers, which causes the polymers to precipitate out. Depending on the choice of polymers, one can get anything from simple Janus particles or layered ones to far more complicated, internally structured particles made by kinetic trapping of nonequilibrium phases.

    ACS Nano 10.1021/acsnano.8b01260 (2018).

  6. Education

    A (dis)course in postdoc identities

    1. Melissa McCartney

    Adapting postdoctoral training to include the development of skills that are translatable to careers outside of the laboratory is critical for diversifying the STEM (science, technology, engineering, and mathematics) workforce. We do not know much about the scientific identities of postdoctoral researchers (postdocs), which could ultimately limit their understanding of additional STEM career opportunities. Price et al. interviewed 30 postdocs to better understand how their scientific identities influenced their career goals. Using discourse analysis, the research team categorized two primary scientific identities among the postdocs: (i) bench scientists, who implement the scientific visions of others, and (ii) principal investigators, who formulate their own scientific visions. A further understanding of how these identities develop is essential for implementing better professional development programs for postdocs as they embark on scientific careers.

    CBE Life Sci. Educ. 10.1187/cbe.17-08-0177 (2018).

  7. Neuroscience

    Overcoming working memory limitations

    1. Peter Stern

    The capacity of our working memory is limited. We normally do not notice these limitations because we use a repertoire of behavioral strategies to overcome them. To investigate how these high-level strategies interact with working memory, Chiang and Wallis trained rhesus macaques to perform a search task and recorded from neurons in their lateral prefrontal cortex. Individual neurons encoded the location of the current search target, as well as the location of other targets several steps earlier or later in the search sequence. Both upcoming targets and previously visited targets were encoded well above chance. However, lateral prefrontal cortical neurons were more likely to encode upcoming targets. Macaques spontaneously used behavioral strategies that helped them solve the task; this improved their performance while simultaneously reducing the neuronal load required.

    Proc. Natl. Acad. Sci. U.S.A. 115, 5010 (2018).