Bacteria and archaea rely on CRISPR (clustered regularly interspaced short palindromic repeats) RNA-guided adaptive immune systems for targeted elimination of foreign nucleic acids. These immune ...systems have been divided into three main types, and the first atomic-resolution structure of a type III RNA-guided immune complex provides new insights into the mechanisms of nucleic acid degradation. Here we compare the crystal structure of a type III complex to recently determined structures of DNA-targeting type I CRISPR complexes. Structural comparisons support previous assertions that type I and type III systems share a common ancestor and reveal how a conserved structural chassis is used to support RNA-, DNA-, or both RNA- and DNA-targeting mechanisms.
Jackson and Wiedenheft review recent structural studies on CRISPR RNA-guided adaptive immune systems and discuss how a conserved structural chassis is used to support RNA-, DNA-, or both RNA- and DNA-targeting mechanisms.
The gastrointestinal microbiome plays a pivotal role in physiological homeostasis of the intestine as well as in the pathophysiology of diseases including inflammatory bowel diseases (IBD) and ...colorectal cancer (CRC). Emerging evidence suggests that gut microbiota signal to the mitochondria of mucosal cells, including epithelial cells and immune cells. Gut microbiota signaling to mitochondria has been shown to alter mitochondrial metabolism, activate immune cells, induce inflammasome signaling, and alter epithelial barrier function. Both dysbiosis of the gut microbiota and mitochondrial dysfunction are associated with chronic intestinal inflammation and CRC. This review discusses mitochondrial metabolism of gut mucosal cells, mitochondrial dysfunction, and known gut microbiota-mediated mitochondrial alterations during IBD and CRC.
The dynamics of carbon monoxide on Cu surfaces was investigated during CO reduction, providing insight into the mechanism leading to the formation of hydrogen, methane, and ethylene, the three key ...products in the electrochemical reduction of CO2. Reaction order experiments were conducted at low temperature in an ethanol medium affording high solubility and surface‐affinity for carbon monoxide. Surprisingly, the methane production rate is suppressed by increasing the pressure of CO, whereas ethylene production remains largely unaffected. The data show that CH4 and H2 production are linked through a common H intermediate and that methane is formed through reactions among adsorbed H and CO, which are in direct competition with each other for surface sites. The data exclude the participation of solution species in rate‐limiting steps, highlighting the importance of increasing surface recombination rates for efficient fuel synthesis.
Understanding hydrocarbon electrosynthesis: Copper can catalyze the reduction of CO2 and CO to hydrocarbons, but does so inefficiently and with poor selectivity. Kinetic measurements indicate that methane and hydrogen formation proceeds via rate‐limiting recombination of surface‐bound intermediates. Tuning the reaction rates between surface‐bound H and CO species, which compete for active sites, is essential for more efficient catalysis.
The omega-3 fatty acids, cis-5, 8, 11, 14, and 17-eicosapentaenoic acid (C20:5; EPA) and cis-4, 7, 10, 13, 16, and 19-docosahexaenoic acid (C22:6; DHA), have wide-ranging benefits in improving heart ...health, immune function, mental health, and infant cognitive development. Currently, the major source for EPA and DHA is from fish oil, and a minor source of DHA is from microalgae. With the increased demand for EPA and DHA, DuPont has developed a clean and sustainable source of the omega-3 fatty acid EPA through fermentation using metabolically engineered strains of Yarrowia lipolytica. In this mini-review, we will focus on DuPont’s technology for EPA production. Specifically, EPA biosynthetic and supporting pathways have been introduced into the oleaginous yeast to synthesize and accumulate EPA under fermentation conditions. This Yarrowia platform can also produce tailored omega-3 (EPA, DHA) and/or omega-6 (ARA, GLA) fatty acid mixtures in the cellular lipid profiles. Fundamental research such as metabolic engineering for strain construction, high-throughput screening for strain selection, fermentation process development, and process scale-up were all needed to achieve the high levels of EPA titer, rate, and yield required for commercial application. Here, we summarize how we have combined the fundamental bioscience and the industrial engineering skills to achieve large-scale production of Yarrowia biomass containing high amounts of EPA, which led to two commercial products, New Harvest™ EPA oil and Verlasso® salmon.
Second language structural priming Jackson, Carrie N.
Second Language Research,
10/2018, Letnik:
34, Številka:
4
Journal Article, Book Review
Recenzirano
The last 15 years has seen a tremendous growth in research on structural priming among second language (L2) speakers. Structural priming is the phenomenon whereby speakers are more likely to repeat a ...structure they have recently heard or produced. Research on L2 structural priming speaks to key issues regarding the underlying linguistic and cognitive mechanisms that support L2 acquisition and use, and the extent to which lexical and grammatical information are shared across an L2 speaker’s languages. As the number of researchers investigating L2 priming and its implications for L2 learning continues to grow, it is important to assess the current state of research in this area and establish directions for continued inquiry. The goal of the current review is to provide an overview of recent research on within-language L2 structural priming, with an eye towards the open questions that remain.
The effect of the proton donor on the kinetics of interfacial concerted proton–electron transfer (CPET) to polycrystalline Au was probed indirectly by studying the rate of hydrogen evolution from ...trialkylammonium donors with different steric profiles, but the same pK a. Detailed kinetic studies point to a mechanism for HER catalysis that involves rate-limiting CPET from the proton donor to the electrode surface, allowing this catalytic reaction to serve as a proxy for the rate of interfacial CPET. In acetonitrile electrolyte, triethylammonium (TEAH+) displays up to 20-fold faster CPET kinetics than diisopropylethylammonium (DIPEAH+) at all measured potentials. In aqueous electrolyte, this steric constraint is largely lifted, suggesting a key role for water in mediating interfacial CPET. In acetonitrile, TEAH+ also displays a much larger transfer coefficient (β = 0.7) than DIPEAH+ (β = 0.4), and TEAH+ displays a potential-dependent H/D kinetic isotope effect that is not observed for DIPEAH+. These results demonstrate that proton donor structure strongly impacts the free energy landscape for CPET to extended solid surfaces and highlight the crucial role of the proton donor in the kinetics of electrocatalytic energy conversion reactions.
Parameters used to describe the electrical properties of organic field-effect transistors, such as mobility and threshold voltage, are commonly extracted from measured current-voltage characteristics ...and interpreted by using the classical metal oxide-semiconductor field-effect transistor model. However, in recent reports of devices with ultra-high mobility (>40 cm(2) V(-1) s(-1)), the device characteristics deviate from this idealized model and show an abrupt turn-on in the drain current when measured as a function of gate voltage. In order to investigate this phenomenon, here we report on single crystal rubrene transistors intentionally fabricated to exhibit an abrupt turn-on. We disentangle the channel properties from the contact resistance by using impedance spectroscopy and show that the current in such devices is governed by a gate bias dependence of the contact resistance. As a result, extracted mobility values from d.c. current-voltage characterization are overestimated by one order of magnitude or more.
Polyelectrolyte brushes provide wear protection and lubrication in many technical, medical, physiological, and biological applications. Wear resistance and low friction are attributed to counterion ...osmotic pressure and the hydration layer surrounding the charged polymer segments. However, the presence of multivalent counterions in solution can strongly affect the interchain interactions and structural properties of brush layers. We evaluated the lubrication properties of polystyrene sulfonate brush layers sliding against each other in aqueous solutions containing increasing concentrations of counterions. The presence of multivalent ions (Y
, Ca
, Ba
), even at minute concentrations, markedly increases the friction forces between brush layers owing to electrostatic bridging and brush collapse. Our results suggest that the lubricating properties of polyelectrolyte brushes in multivalent solution are hindered relative to those in monovalent solution.
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