203 research outputs found
General one-loop formulas for decay
Radiative corrections to the 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 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 methionineābinding protein MetQ in substrate-free form and bound to L- and D-methionine isomers
The bacterial periplasmic methionineābinding 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 substrateāfree form of MetQ, and detailing how MetQ binds multiple methionine derivatives, including both Lā and Dāmethionine isomers. In this study, we report the structures of the Neisseria meningitides MetQ in substrateāfree form and in complexes with Lāmethionine and with Dāmethionine, along with the associated binding constants determined by isothermal titration calorimetry. Structures of the substrateāfree (N238A) and substrateābound N. meningitides MetQ are related by a āVenusāfly trapā hingeātype movement of the two domains accompanying methionine binding and dissociation. Lāmethionine and Dāmethionine 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 ligandāfree 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
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 methionineābinding protein MetQ in substrate-free form and bound to L- and D-methionine isomers
The bacterial periplasmic methionineābinding 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 substrateāfree form of MetQ, and detailing how MetQ binds multiple methionine derivatives, including both Lā and Dāmethionine isomers. In this study, we report the structures of the Neisseria meningitides MetQ in substrateāfree form and in complexes with Lāmethionine and with Dāmethionine, along with the associated binding constants determined by isothermal titration calorimetry. Structures of the substrateāfree (N238A) and substrateābound N. meningitides MetQ are related by a āVenusāfly trapā hingeātype movement of the two domains accompanying methionine binding and dissociation. Lāmethionine and Dāmethionine 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 ligandāfree 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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