458 research outputs found

    The 3.4-kDa Ost4 protein is required for the assembly of two distinct oligosaccharyltransferase complexes in yeast

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    In the central reaction of N-linked glycosylation, the oligosaccharyltransferase (OTase) complex catalyzes the transfer of a lipid-linked core oligosaccharide onto asparagine residues of nascent polypeptide chains in the lumen of the endoplasmic reticulum (ER). The Saccharomyces cerevisiae OTase has been shown to consist of at least eight subunits. We analyzed this enzyme complex, applying the technique of blue native gel electrophoresis. Using available antibodies, six different subunits were detected in the wild-type (wt) complex, including Stt3p, Ost1p, Wbp1p, Swp1p, Ost3p, and Ost6p. We demonstrate that the small 3.4-kDa subunit Ost4p is required for the incorporation of either Ost3p or Ost6p into the complex, resulting in two, functionally distinct OTase complexes in vivo. Ost3p and Ost6p are not absolutely required for OTase activity, but modulate the affinity of the enzyme toward different protein substrate

    Zener transitions between dissipative Bloch bands. II: Current Response at Finite Temperature

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    We extend, to include the effects of finite temperature, our earlier study of the interband dynamics of electrons with Markoffian dephasing under the influence of uniform static electric fields. We use a simple two-band tight-binding model and study the electric current response as a function of field strength and the model parameters. In addition to the Esaki-Tsu peak, near where the Bloch frequency equals the damping rate, we find current peaks near the Zener resonances, at equally spaced values of the inverse electric field. These become more prominenent and numerous with increasing bandwidth (in units of the temperature, with other parameters fixed). As expected, they broaden with increasing damping (dephasing).Comment: 5 pages, LateX, plus 5 postscript figure

    Исследование огнезащищенных фанерных плит на горючесть и токсичность

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    Ціль роботи порівняльне вивчення звичайних фанерних плит, а також просочених вогнебіозахистною сумішю, яка складається із суміши сольового антипирену та полімерного антисептика ДСА 2, а також гідрофобізуючого препарату «Силол» на горючість та токсичність. В ході роботы було показано, що фанерна плита, яку оброблено вогнебіозахистною сумішю, по показникам горючості та токсич ності значно превосходить не оброблену фанеру.The target of the work is comparative study of plywood — ordinary and pretreated by salt fire retardant and polymeric antiseptic ДСА 2 mixture with hydrophobying composition «Силол» — for the combustibility and the toxicity. It was shown that pretreated plywood is more toxic and less combustible

    Clumped isotope evidence for episodic, rapid flow of fluids in a mineralized fault system in the Peak District, UK

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    We have used clumped isotope thermometry to study a fault-hosted hydrothermal calcite vein associated with the Mississippi Valley Type (MVT) mineralization on the Derbyshire Platform in the southern Pennines, UK. This is the first published dataset obtained using a new mass spectrometer, MIRA, optimized for clumped isotope analysis and an associated clumped isotope-temperature calibration. We analysed multiple generations of vein growth at high spatial resolution in two transects across the vein. The vein grew episodically at temperatures between 40 and 100°C. We interpret each episode of growth as being associated with an increasing flux of formation waters from deep sedimentary basins next to the mineralized platform and an accompanying increase in the precipitation temperatures. Heat is conserved in the fluid as it ascends along the fault surface and, thus, flow must have been fast and restricted to short-lived pulses. The flux could have been driven by high pore pressures associated with rapid sedimentation, hydrocarbon generation and diagenesis in the basinal facies of the Visean Bowland-Hodder group. Natural hydraulic fracturing of shale units and failure of capillary seals, possibly triggered by uplift, allowed the release of fluids into aquifers within the sediment pile. The transmission of high pore fluid pressures from the shales to the fault zone, aided by the compressibility of the gas phase in two-phase pore fluids, may have resulted in fault rupture, accompanied by enhanced fracture permeability and rapid fluid flow. Vein growth ceased as pore pressures dissipated. Such behaviour is closely related to a seismic valve type model for mineralization

    Computational characterization of the binding mode and mechanism of action of tricyclic small molecules at 5-HT1E and 5-HT1F receptors

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    5-hydroxytryptamine (serotonin) 1E and 1F receptors (5-HT1E and 5-HT1F, respectively) are highly expressed human G protein-coupled receptors with high sequence identity among themselves and other 5-HT1 receptor subtypes. Although the physiological role of 5-HT1E and 5-HT1F is not fully understood, they are molecular targets of drugs that are effective to treat migraine, depression, and schizophrenia, albeit not without also producing adverse effects. Notably, no selective or high-affinity drugs have been reported for the 5-HT1E receptor to date. Thus, there is widespread interest in understanding at an atomic level of detail how small molecules bind and activate these receptors for the ultimate purpose of designing improved therapeutics. Through computational studies including docking calculations, metadynamics rescoring, and molecular dynamics simulations of cryo-electron microscopy structures, we predict the binding mode and mechanism of action of tricyclic small molecules that are capable of simultaneously activating the 5-HT1E and 5-HT1F receptors. Our results provide testable hypotheses of ligand-receptor interactions and ligand-induced allosteric modulation that may be used to improve the efficacy of these small molecules towards specific biological endpoints

    Simplified Models for LHC New Physics Searches

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    This document proposes a collection of simplified models relevant to the design of new-physics searches at the LHC and the characterization of their results. Both ATLAS and CMS have already presented some results in terms of simplified models, and we encourage them to continue and expand this effort, which supplements both signature-based results and benchmark model interpretations. A simplified model is defined by an effective Lagrangian describing the interactions of a small number of new particles. Simplified models can equally well be described by a small number of masses and cross-sections. These parameters are directly related to collider physics observables, making simplified models a particularly effective framework for evaluating searches and a useful starting point for characterizing positive signals of new physics. This document serves as an official summary of the results from the "Topologies for Early LHC Searches" workshop, held at SLAC in September of 2010, the purpose of which was to develop a set of representative models that can be used to cover all relevant phase space in experimental searches. Particular emphasis is placed on searches relevant for the first ~50-500 pb-1 of data and those motivated by supersymmetric models. This note largely summarizes material posted at http://lhcnewphysics.org/, which includes simplified model definitions, Monte Carlo material, and supporting contacts within the theory community. We also comment on future developments that may be useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results from "Topologies for Early LHC Searches" workshop (SLAC, September 2010). Supplementary material can be found at http://lhcnewphysics.or

    Neue Parteiführung in China: Generationswechsel aufgeschoben

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    Nach Monaten der Spekulationen im In- und Ausland ist seit dem 15. November endlich klar, wer für die nächsten fünf Jahre an der Spitze Chinas stehen wird. Vorausgegangen war ein Tauziehen der verschiedenen Seilschaften in der Parteiführung. Der innerste Zirkel der Partei, der Ständige Ausschuss des Politbüros, wurde verkleinert und ist relativ homogen mit Gefolgsleuten des früheren Parteivorsitzenden Jiang Zemin besetzt, darunter der neue Parteichef Xi Jinping. Einzig der wahrscheinliche neue Premierminister Li gilt als Parteigänger des abgetretenen Hu Jintao. Die neue Führungsriege lässt kaum auf den entschiedenen Willen zu wirtschaftlichen oder politischen Reformen schließen. (Autorenreferat
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