Transient kinetics of chemical reactions with bounded diffusion perpendicular to the reaction coordinate: Intramolecular processes with slow conformational changes

1983 ◽  
Vol 78 (11) ◽  
pp. 6947-6959 ◽  
Author(s):  
Noam Agmon ◽  
J. J. Hopfield
Keyword(s):  
Chemical Reactions ◽  
Conformational Changes ◽  
Reaction Coordinate ◽  
Transient Kinetics ◽  
Kinetics Of

Transient Kinetics of the Acetylcholinesterase Catalyzed Hydrolysis of N-Methylindoxyl Acetate

1975 ◽  
Vol 53 (3) ◽  
pp. 380-387 ◽  
Author(s):  
M. H. Sadar ◽  
K. J. Laidler
Keyword(s):  
Steady State ◽  
Conformational Change ◽  
Conformational Changes ◽  
Transient Kinetics ◽  
Concerted Mechanism ◽  
Electric Eel ◽  
Fast Transient ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Addition

An experimental study has been made of the kinetics of the hydrolysis of N-methylindoxyl acetate catalyzed by electric-eel acetylcholinesterase, both in the steady state and the pre-steady state. Stopped-flow and temperature-jump experiments revealed a fast transient and a slow one. The fast transient is correlated with the conventional mechanism [Formula: see text]. The slow transient is attributed to conformational changes involving E or EA. Analysis of it revealed two exponential terms of the form e−λt, and the two λ values were obtained over the temperature range 5.0 to 25.0 °C. The results are interpreted in terms of two alternative mechanisms; in one, the enzyme undergoes a conformational change before it adds on the substrate molecule; in the other, the conformational change occurs after the substrate addition. Both mechanisms may be involved, but the results exclude a concerted mechanism in which the conformational change occurs concurrently with the addition of substrate. Kinetic parameters (ΔS≠ and E) are obtained for this conformational change and for the conversion of EA into EA′ + X.

New highly efficient coulometric cell with homogenous potential distribution on the working electrode

1986 ◽  
Vol 51 (3) ◽  
pp. 636-642
Author(s):  
Michal Németh ◽  
Ján Mocák
Keyword(s):  
Chemical Reactions ◽  
Potential Distribution ◽  
Anaerobic Conditions ◽  
Highly Efficient ◽  
Working Electrode ◽  
Constant Potential ◽  
Quantitative Analyses ◽  
Mechanism And Kinetics ◽  
Kinetics Of

A highly efficient coulometric cell was designed and constructed, ensuring a constant potential over the whole surface of the working electrode and suitable for very rapid electrolysis. It consists of concentric cylindrical Teflon parts; also the working and auxiliary electrodes are cylindrical and concentric. Electrolysis can be carried out under anaerobic conditions. Functioning of the cell was tested on the oxidation of hexacyanoferrate(II) and chlorpromazine and reduction of hexacyanoferrate(III). The new cell is suitable for routine quantitative analyses and in studying the mechanism and kinetics of moderately rapid chemical reactions.

The Energy Gap as a Universal Reaction Coordinate for the Simulation of Chemical Reactions

2009 ◽  
Vol 113 (22) ◽  
pp. 7867-7873 ◽  
Author(s):  
Letif Mones ◽  
Petr Kulhánek ◽  
István Simon ◽  
Alessandro Laio ◽  
Monika Fuxreiter
Keyword(s):  
Chemical Reactions ◽  
Energy Gap ◽  
Reaction Coordinate

Transient kinetics of ATP hydrolysis by covalently crosslinked actomyosin complex in water and 40% ethylene glycol by the rapid flow quench method

Biochemistry ◽  
1985 ◽  
Vol 24 (14) ◽  
pp. 3814-3820 ◽  
Author(s):  
J. A. Biosca ◽  
F. Travers ◽  
T. E. Barman ◽  
R. Bertrand ◽  
E. Audemard ◽  
...  
Keyword(s):  
Ethylene Glycol ◽  
Atp Hydrolysis ◽  
Transient Kinetics ◽  
Actomyosin Complex ◽  
Rapid Flow ◽  
Kinetics Of ◽  
Quench Method

scholarly journals Structure–Function Relations of the First and Fourth Predicted Extracellular Linkers of the Type IIa Na+/Pi Cotransporter

2004 ◽  
Vol 124 (5) ◽  
pp. 475-488 ◽  
Author(s):  
Colin Ehnes ◽  
Ian C. Forster ◽  
Katja Kohler ◽  
Andrea Bacconi ◽  
Gerti Stange ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Reaction Rates ◽  
Transport Pathway ◽  
Extracellular Medium ◽  
Voltage Range ◽  
Substituted Cysteine Accessibility ◽  
Voltage Dependent ◽  
Opposite Behavior ◽  
Rate Limiting ◽  
Kinetics Of

The putative first intracellular and third extracellular linkers are known to play important roles in defining the transport properties of the type IIa Na+-coupled phosphate cotransporter (Kohler, K., I.C. Forster, G. Stange, J. Biber, and H. Murer. 2002b. J. Gen. Physiol. 120:693–705). To investigate whether other stretches that link predicted transmembrane domains are also involved, the substituted cysteine accessibility method (SCAM) was applied to sites in the predicted first and fourth extracellular linkers (ECL-1 and ECL-4). Mutants based on the wild-type (WT) backbone, with substituted novel cysteines, were expressed in Xenopus oocytes, and their function was assayed by isotope uptake and electrophysiology. Functionally important sites were identified in both linkers by exposing cells to membrane permeant and impermeant methanethiosulfonate (MTS) reagents. The cysteine modification reaction rates for sites in ECL-1 were faster than those in ECL-4, which suggested that the latter were less accessible from the extracellular medium. Generally, a finite cotransport activity remained at the end of the modification reaction. The change in activity was due to altered voltage-dependent kinetics of the Pi-dependent current. For example, cys substitution at Gly-134 in ECL-1 resulted in rate-limiting, voltage-independent cotransport activity for V ≤ −80 mV, whereas the WT exhibited a linear voltage dependency. After cys modification, this mutant displayed a supralinear voltage dependency in the same voltage range. The opposite behavior was documented for cys substitution at Met-533 in ECL-4. Modification of cysteines at two other sites in ECL-1 (Ile-136 and Phe-137) also resulted in supralinear voltage dependencies for hyperpolarizing potentials. Taken together, these findings suggest that ECL-1 and ECL-4 may not directly form part of the transport pathway, but specific sites in these linkers can interact directly or indirectly with parts of NaPi-IIa that undergo voltage-dependent conformational changes and thereby influence the voltage dependency of cotransport.

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