195 research outputs found

    General one-loop formulas for decay hā†’ZĪ³h\rightarrow Z\gamma

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    Radiative corrections to the hā†’ZĪ³h\rightarrow Z\gamma are evaluated in the one-loop approximation. The unitary gauge gauge is used. The analytic result is expressed in terms of the Passarino-Veltman functions. The calculations are applicable for the Standard Model as well for a wide class of its gauge extensions. In particular, the decay width of a charged Higgs boson HĀ±ā†’WĀ±Ī³H^\pm \rightarrow W^\pm\gamma can be derived. The consistence of our formulas and several specific earlier results is shown.Comment: 33 pages, 3 figures, a new section (V) and references were improved in the published versio

    Structures of the Neisseria meningitides methionineā€binding protein MetQ in substrate-free form and bound to L- and D-methionine isomers

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    The bacterial periplasmic methionineā€binding protein MetQ is involved in the import of methionine by the cognate MetNI methionine ABC transporter. The MetNIQ system is one of the few members of the ABC importer family that has been structurally characterized in multiple conformational states. Critical missing elements in the structural analysis of MetNIQ are the structure of the substrateā€free form of MetQ, and detailing how MetQ binds multiple methionine derivatives, including both Lā€ and Dā€methionine isomers. In this study, we report the structures of the Neisseria meningitides MetQ in substrateā€free form and in complexes with Lā€methionine and with Dā€methionine, along with the associated binding constants determined by isothermal titration calorimetry. Structures of the substrateā€free (N238A) and substrateā€bound N. meningitides MetQ are related by a ā€œVenusā€fly trapā€ hingeā€type movement of the two domains accompanying methionine binding and dissociation. Lā€methionine and Dā€methionine bind to the same site on MetQ, and this study emphasizes the important role of asparagine 238 in ligand binding and affinity. A thermodynamic analysis demonstrates that ligandā€free MetQ associates with the ATP bound form of MetNI ~40 times more tightly than does liganded MetQ, consistent with the necessity of dissociating methionine from MetQ for transport to occur

    The H-1 and C-13 chemical shifts of 5-5 lignin model dimers : An evaluation of DFT functionals

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    The calculations of H-1 and C-13 NMR chemical shifts were performed on three 5-5 lignin dimers, prominent substructures in softwood lignins, to compare with experimental data. Initially, 10 DFT functionals (B3LYP, B3PW91, BPV86, CAM-B3LYP, HCTH, HSEH1PBE, mPW1PW91, PBEPBE, TPSSTPSS, and omega B97XD) combined with the gage-including atomic orbital (GIAO) method and basic set 6-31G(d,p) were tested on 3,3'-(6,6'-dihydroxy-5,5'-dimethoxy-[1,1'-biphenyl]-3,3'-diyl)dipropionic acid (1), efficiently synthesized from ferulic acid. HSEH1PBE, mPW1PW91, and omega B97XD were found to be the three best performing functionals with strong correlations (r(2) >= 0.9988) and low errors (CMAEsPeer reviewe

    Structures of the Neisseria meningitides methionineā€binding protein MetQ in substrate-free form and bound to L- and D-methionine isomers

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    The bacterial periplasmic methionineā€binding protein MetQ is involved in the import of methionine by the cognate MetNI methionine ABC transporter. The MetNIQ system is one of the few members of the ABC importer family that has been structurally characterized in multiple conformational states. Critical missing elements in the structural analysis of MetNIQ are the structure of the substrateā€free form of MetQ, and detailing how MetQ binds multiple methionine derivatives, including both Lā€ and Dā€methionine isomers. In this study, we report the structures of the Neisseria meningitides MetQ in substrateā€free form and in complexes with Lā€methionine and with Dā€methionine, along with the associated binding constants determined by isothermal titration calorimetry. Structures of the substrateā€free (N238A) and substrateā€bound N. meningitides MetQ are related by a ā€œVenusā€fly trapā€ hingeā€type movement of the two domains accompanying methionine binding and dissociation. Lā€methionine and Dā€methionine bind to the same site on MetQ, and this study emphasizes the important role of asparagine 238 in ligand binding and affinity. A thermodynamic analysis demonstrates that ligandā€free MetQ associates with the ATP bound form of MetNI ~40 times more tightly than does liganded MetQ, consistent with the necessity of dissociating methionine from MetQ for transport to occur
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