Protonation of the binuclear metal center within the active site of phosphotriesterase
-
PubMed
(0) (0 Votes)Views: (1013)
Date: (27-01-09)
Pages: () Author: Samples CR, Howard T, Raushel FM, DeRose VJ.
-
Abstract:Protonation of the binuclear metal center within the active site of phosphotriesterase. Samples CR, Howard T, Raushel FM, DeRose VJ. Department of Chemistry, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012, USA. Phosphotrieste rase (PTE) is a binuclear metalloenzyme that catalyzes the hydrolysis of organophosphates, including pesticides and chemical warfare agents, at rates approaching the diffusion controlled limit. The catalytic mechanism of this enzyme features a bridging solvent molecule that is proposed to initiate nucleophilic attack at the phosphorus center of the substrate. X-band EPR spectroscopy is utilized to investigate the active site of Mn/Mn-substituted PTE. Simulation of the dominant EPR spectrum from the coupled binuclear center of Mn/Mn-PTE requires slightly rhombic zero-field splitting parameters. Assuming that the signal arises from the S = 2 manifold, an exchange coupling constant of J = -2.7 +/- 0.2 cm(-)(1) (H(ex) = -2JS(1) x S(2)) is calculated. A kinetic pK(a) of 7.1 +/- 0.1 associated with loss in activity at low pH indicates that a protonation event is responsible for inhibition of catalysis. Analysis of changes in the EPR spectrum as a function of pH provides a pK(a) of 7.3 +/- 0.1 that is assigned as the protonation of the hydroxyl bridge. From the comparison of kinetic and spectral pK(a) values, it is concluded that the loss of catalytic activity at acidic pH results from the protonation of the hydroxide that bridges the binuclear metal center. PMID: 16101284 [PubMed - indexed for MEDLINE]
-
Effect of protonation on the nanoalloying of lithium niobate
Abstract The results on protonation in solutions and melts of salts and acids, as well as structural changes associated with the formation of nanocomposition (NC) structure of materials are presented. The associated protonation is a necessary condition for proton separation of structural units (PSU) in NC structure model. The shape and size of PSU in simple substances and compounds and their variation in phase transition have been determined with the use of modified formula of cinematic diffraction theory applied to minimal scattering volumes....
-
Effect of protonation on the nanoalloying of lithium niobate
Abstract The results on protonation in solutions and melts of salts and acids, as well as structural changes associated with the formation of nanocomposition (NC) structure of materials are presented. The associated protonation is a necessary condition for proton separation of structural units (PSU) in NC structure model. The shape and size of PSU in simple substances and compounds and their variation in phase transition have been determined with the use of modified formula of cinematic diffraction theory applied to minimal scattering volumes....
-
Protonation of ketoconazole in relation to fungistatic activity
Protonation of ketoconazole in relation to fungistatic activity. Beggs WH. PMID: 1766459 [PubMed - indexed for MEDLINE]
-
Creation of nanopatterns by local protonation of P4VP via dip pen nanolithograph...
Abstract The elastic mechanical response of a poly(4-vinylpyridine) film is exploited to create nanostructures under ambient conditions via dip pen nanolithography. Using a pH 4 phosphate buffer solution as the "ink," a series of experimental results indicates that the nanometer-sized structures are due to local swelling of the film's pyridyl groups upon their protonation with the hydronium ions delivered by the tip. Control over the structures' height is gained by properly selecting the writing velocities or the dwell time, respectively.
-
Protonation and doping behavior of polypyrrole films and powders
Abstract Not Available
-
Protonation-triggered conformational changes to m?bius aromatic 32heptaphyrins11...
Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, Japan.
-
Heme-linked protonation of HCN CO NO and O2 complexes of reduced horseradish per...
PMID: 971 [PubMed - indexed for MEDLINE]
-
Formation of dodecaphenylporphodimethene via facile protonation of saddle-distor...
Department of Material and Life Science, Graduate School of Engineering, Osaka University and SORST (JST), 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan. kojima@chem.eng.osaka-u.ac.jp (T. K.) fukuzumi@chem.eng.osaka-u.ac.jp (S. F.).
-
Quantitative treatments of protonation equilibria shifts in micellar systems
Quantitative treatments of protonation equilibria shifts in micellar systems. Minero C, Pelizzetti E. Dipartimento di Chimica Analitica, Universit? di Torino, Italy. The paper reviews the theoretical models and equations used for the interpretation of weak acid dissociation equilibria in the presence of micellar systems. The models and the equations of the literature can be rewritten and reinterpreted in terms of the generalized pseudophase model, for which the basic equations are reported. Some new relationships for the titration of weak ac...
-
Specific ion effects Role of salt and buffer in protonation of cytochrome c
Specific ion effects: Role of salt and buffer in protonation of cytochrome c. Bostr?m M, Williams DR, Ninham BW. Department of Physics and Measurement Technology, Link?ping University, Sweden. mabos@ifm.liu.se Changes in background salt and buffer are known to influence the properties of proteins. The reasons have remained obscure. The challenge posed by many such problems is this. Can physical chemistry contribute any predictive quantitative insights to what is in effect the simplest macromolecular solution behavior? Or must all remain spec...
RSS Feeds |
Help & Info |
C2007 sciencestage.com |
|||
|---|---|---|---|---|---|
