Quantum mechanical/molecular mechanical methods and the study of kinetic isotope effects: modelling the covalent junction region and application to the enzyme xylose isomerase

2001 ◽  
Vol 106 (1-2) ◽  
pp. 105-112 ◽  
Author(s):  
R. Mark Nicoll ◽  
Sally A. Hindle ◽  
Grant MacKenzie ◽  
Ian H. Hillier ◽  
Neil A. Burton
Keyword(s):  
Isotope Effects ◽  
Xylose Isomerase ◽  
Kinetic Isotope Effects ◽  
Quantum Mechanical ◽  
Junction Region ◽  
Kinetic Isotope ◽  
Mechanical Methods

Semiclassical and Quantum Mechanical Calculations of Isotopic Kinetic Branching Ratios for the Reactionof O(3P) with HD

1989 ◽  
Vol 44 (5) ◽  
pp. 427-434 ◽  
Author(s):  
Gillian C. Lynch ◽  
Philippe Halvick ◽  
Donald G. Truhlar ◽  
Bruce C. Garrett ◽  
David W. Schwenke ◽  
...  
Keyword(s):  
Transition State Theory ◽  
Energy Surface ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Branching Ratios ◽  
State Theory ◽  
Quantum Mechanical ◽  
Variational Transition State Theory ◽  
Least Action ◽  
Kinetic Isotope

Tunneling probabilities for the reactions O + HD → OH + D and O + DH → OD + H have been calculated by semiclassical dynamical methods and compared to accurate quantal calculations for the same potential energy surface. The results are used to test the reliability of variational transition state theory with the least-action semiclassical method for tunneling probabilities for the prediction of intramolecular kinetic isotope effects.

scholarly journals Can Alkaline Hydrolysis of γ-HCH Serve as a Model Reaction to Study Its Aerobic Enzymatic Dehydrochlorination by LinA?

2019 ◽  
Vol 20 (23) ◽  
pp. 5955 ◽  
Author(s):  
Suraj Kannath ◽  
Paweł Adamczyk ◽  
Langping Wu ◽  
Hans H. Richnow ◽  
Agnieszka Dybala-Defratyka
Keyword(s):  
Isotope Fractionation ◽  
Isotope Effects ◽  
Aqueous Media ◽  
Kinetic Isotope Effects ◽  
Umbrella Sampling ◽  
Quantum Mechanical ◽  
Enzymatic Reactions ◽  
Kinetic Isotope ◽  
Hydroxyl Ion ◽  
Fractionation Analysis

Hexachlorocyclohexane (HCH) isomers constitute a group of persistent organic pollutants. Their mass production and treatment have led to a global environmental problem that continues to this day. The characterization of modes of degradation of HCH by isotope fractionation is a current challenge. Multi isotope fractionation analysis provides a concept to characterize the nature of enzymatic and chemical transformation reactions. The understanding of the kinetic isotope effects (KIE) on bond cleavage reaction contributes to analyses of the mechanism of chemical and enzymatic reactions. Herein, carbon, chlorine, and hydrogen kinetic isotope effects are measured and predicted for the dehydrochlorination reaction of γ-HCH promoted by the hydroxyl ion in aqueous solution. Quantum mechanical (QM) microsolvation with an implicit solvation model and path integral formalism in combination with free-energy perturbation and umbrella sampling (PI-FEP/UM) and quantum mechanical/molecular mechanical QM/MM potentials for including solvent effects as well as calculating isotope effects are used and analyzed with respect to their performance in reproducing measured values. Reaction characterization is discussed based on the magnitudes of obtained isotope effects. The comparative analysis between the chemical dehydrochlorination of γ-HCH in aqueous media and catalyzed reaction by dehydrochlorinase, LinA is presented and discussed. Based on the values of isotope effects, these two processes seem to occur via the same net mechanism.

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