4,029 research outputs found

    S-adenosyl-l-methionine: (S) -7,8,13, 14-tetrahydroberberine--n-methyltransferase, a branch point enzyme in the biosynthesis of benzophenanthridine and protopine alkaloids.

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    The enzyme which transfers the CH3-group of S-adenosylmethionine to the nitrogen atom of (S)-tetrahydroberberine and (S)-stylopine is found to occur in a number of plant cell cultures originating from species containing alkaloids; it is located at an important branch point in isoquinoline alkaloid biosynthesis

    Quasiparticle Self-Consistent GW Theory

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    In past decades the scientific community has been looking for a reliable first-principles method to predict the electronic structure of solids with high accuracy. Here we present an approach which we call the quasiparticle self-consistent GW approximation (QpscGW). It is based on a kind of self-consistent perturbation theory, where the self-consistency is constructed to minimize the perturbation. We apply it to selections from different classes of materials, including alkali metals, semiconductors, wide band gap insulators, transition metals, transition metal oxides, magnetic insulators, and rare earth compounds. Apart some mild exceptions, the properties are very well described, particularly in weakly correlated cases. Self-consistency dramatically improves agreement with experiment, and is sometimes essential. Discrepancies with experiment are systematic, and can be explained in terms of approximations made.Comment: 12 pages, 3 figure

    Enzymatic formation of protopines by a microsomal cytochrome P-450 system of Corydalis vaginans

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    A microsomal cytochrome P-450-NADPH dependent enzyme which hydroxylates stereo- and regiospecifically carbon atom 14 of (S)- -N- methyltetrahydroprotoberberines has been discovered in a number of plant cell cultures originating from species containing protopine alkaloids; the monooxygenase was solubilized, partially purified (100-fold) and characterized

    Maxwell stress in fluid mixtures

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    We examine the structure of Maxwell stress in binary fluid mixtures under an external electric field and discuss its consequence. In particular, we show that, in immiscible blends, it is intimately related to the statistics of domain structure. This leads to a compact formula, which may be useful in the investigation of electro-rheological effects in such systems. The stress tensor calculated in a phase separated fluid under a steady electric field is in a good agreement with recent experiments.Comment: 5 page

    Many-body Electronic Structure of Metallic alpha-Uranium

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    We present results for the electronic structure of alpha uranium using a recently developed quasiparticle self-consistent GW method (QSGW). This is the first time that the f-orbital electron-electron interactions in an actinide has been treated by a first-principles method beyond the level of the generalized gradient approximation (GGA) to the local density approximation (LDA). We show that the QSGW approximation predicts an f-level shift upwards of about 0.5 eV with respect to the other metallic s-d states and that there is a significant f-band narrowing when compared to LDA band-structure results. Nonetheless, because of the overall low f-electron occupation number in uranium, ground-state properties and the occupied band structure around the Fermi energy is not significantly affected. The correlations predominate in the unoccupied part of the f states. This provides the first formal justification for the success of LDA and GGA calculations in describing the ground-state properties of this material.Comment: 4 pages, 3 fihgure

    Notes on the Hamiltonian formulation of 3D Yang-Mills theory

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    Three-dimensional Yang-Mills theory is investigated in the Hamiltonian formalism based on the Karabali-Nair variable. A new algorithm is developed to obtain the renormalized Hamiltonian by identifying local counterterms in Lagrangian with the use of fictitious holomorphic symmetry existing in the framework with the KN variable. Our algorithm is totally algebraic and enables one to calculate the ground state wave functional recursively in gauge potentials. In particular, the Gaussian part thus calculated is shown to coincide with that obtained by Leigh et al. Higher-order corrections to the Gaussian part are also discussed.Comment: 26 pages, LaTeX; discussions on IR regulators and local counterterms improved, references adde
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