Bjerrum–Brönsted Prediction of Ionic‐Strength Independence of Some Multi‐ionic Reaction Rates

1968 ◽  
Vol 48 (10) ◽  
pp. 4806-4806 ◽  
Author(s):  
D. R. Rosseinsky
Keyword(s):  
Ionic Strength ◽  
Reaction Rates ◽  
Ionic Reaction

scholarly journals Effective electrostatic charge of coagulation factor X in solution and on phospholipid membranes: implications for activation mechanisms and structure–function relationships of the Gla domain

1998 ◽  
Vol 330 (1) ◽  
pp. 533-539 ◽  
Author(s):  
P. Maria McGEE ◽  
Hoa TEUSCHLER ◽  
Jie LIANG
Keyword(s):  
Ionic Strength ◽  
Electrostatic Interactions ◽  
Specific Interaction ◽  
Geometric Analysis ◽  
Factor Xa ◽  
Coagulation Factor ◽  
Reaction Rates ◽  
Phase Cell ◽  
Factor X ◽  
Gla Domain

Electrostatic interactions during activation of coagulation factor X were analysed by comparing effects of ionic strength on reaction rates with predictions of classical electrostatic theory. Geometrical correlations were investigated using alpha-shape-based computations on the crystal structure of Ca-fragment 1 of prothrombin. The ionic strength of the reaction environment was controlled with different univalent salts including NaCl, KCl, CsCl, LiCl, NaI, NaBr and KI. Reactions were assembled in three different environments: aqueous phase, cell membranes and synthetic TF/PS/PC (tissue factor relipidated in 30% phosphatidylserine, 70% phosphatidylcholine) vesicles. Reaction rates were measured at pH 7.2, 4 mM CaCl2 and 33 °C, using chromogenic substrate to follow factor Xa generation. Rates decreased with increasing concentration of univalent salt, and the magnitude of the decrease was independent of salt type. On the basis of electrostatic relationships on PS/PC vesicles, the effective charge on factor X was +1.5, and the PS/factor X stoichiometry was 2.28. Structural analysis of the γ-carboxyglutamic acid (Gla) domain revealed three surface pockets, forming potential sites for Ca2+ binding, with distinct spatial orientations. Interpreted together, the results of the geometric analysis and the measured effective charges suggest an efficient electrostatic mechanism for capture and retention of substrates by procoagulant membranes. Non-specific and delocalized interaction between the membrane and each one of the charged facets of the Gla domain can increase the probability of substrate binding, while allowing rotational and translational mobility of substrate for specific interaction with the enzyme.

scholarly journals Oxidative degradation of some antibiotics by permanganate ion in alkaline medium: A kinetic and mechanistic approach

2020 ◽  
Vol 19 (9) ◽  
pp. 1999-2007
Author(s):  
Ahmed Fawzy ◽  
Metwally Abdallah ◽  
Nada Alqarni
Keyword(s):  
Ionic Strength ◽  
Alkaline Medium ◽  
Degradation Kinetics ◽  
Oxidative Degradation ◽  
Reaction Rates ◽  
Oxidation Products ◽  
Significant Treatment ◽  
First Order ◽  
Hydroxyl Ion ◽  
Permanganate Ion

Purpose: To investigate the kinetics of oxidative removal of two β-lactam antibiotics (A), namely, ampicillin and flucloxacillin.Methods: In this study, permanganate ion (MnO4-) was used as an oxidant in an alkaline medium at fixed ionic strength of 0.1 mol dm-3 and a temperature of 298 K utilizing a spectrophotometric technique. The obtained oxidation products were characterized using spot tests and FT-IR spectra.Results: The stoichiometry of the reactions was 1:4 (A : MnO4-). The reactions were a first order credence in [MnO4-] and fractional-first order  kinetics in antibiotic and hydroxyl ion. Influence of ionic strength was successfully explored. Dependence of reaction rates on temperature was studied and the activation parameters were computed and discussed. A plausible mechanism for the oxidation reactions has been elucidated. A consistent rate-law expression was also derived.Conclusion: This study introduces a significant treatment method for antibiotic removal, thus helping to protect the environment and human health. Keywords: Permanganate, Antibiotics, Oxidative degradation, Kinetics, Mechanism

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