Role of tyrosine 143 in lactate dehydrogenation by flavocytochrome b2. Primary kinetic isotope effect studies with a phenylalanine mutant

Biochemistry ◽  
1994 ◽  
Vol 33 (3) ◽  
pp. 798-806 ◽  
Author(s):  
Nathalie Rouviere-Fourmy ◽  
Chantal Capeillere-Blandin ◽  
Florence Lederer
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Flavocytochrome B2 ◽  
Kinetic Isotope

Kinetic Isotope Effect Studies on the Reaction of Benzyl Nitrate with Base in Varions Solvents

1971 ◽  
Vol 49 (23) ◽  
pp. 3856-3865 ◽  
Author(s):  
Carol A. Pollock ◽  
P. J. Smith
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Nitrogen Isotope ◽  
Minor Role ◽  
Solvent Mixtures ◽  
Elimination Reaction ◽  
Kinetic Isotope ◽  
Role Of Solvent

The role of solvent and base on the nature of the transition state for the concerted one-step carbonyl elimination reaction of benzyl nitrate has been examined using rate and kinetic isotope effect techniques. The primary hydrogen–deuterium isotope effect was found to increase with increasing strength of the abstracting base, kH/kD = 5.94 and 6.41 at 30° for reaction with EtO−/EtOH and t-BuO−/t-BuOH, respectively. The nitrogen isotope effect decreased with increasing strength of the abstracting base, 2.07, 1.82, and 1.54% for reaction with OH−/40 vol % EtOH–H2O, EtO−/EtOH, and t-BuO−/t-BuOH, respectively. The conclusion is reached that an increase in the strength of the abstracting base leads to a more reactant-like transition state with decreased rupture of both the C—H and O—N bonds. The role of solvent on the nature of the transition state was examined by determining rates and nitrogen isotope effects for reaction in various ethanol–water and ethanol–dimethyl sulfoxide mixtures. The nitrogen effect was found to remain essentially constant in solvent mixtures ranging from 65 vol % EtOH–H2O on the one hand to 80 vol% EtOH–DMSO on the other hand where the rate constants differed by a factor of 100 fold. It is concluded that solvent plays only a very minor role in determining transition state structure for the concerted elimination reaction of a neutral substrate with base.

Exact quantum calculations of the kinetic isotope effect: Cross sections and rate constants for the F+HD reaction and role of tunneling

2006 ◽  
Vol 125 (13) ◽  
pp. 133109 ◽  
Author(s):  
Dario De Fazio ◽  
Vincenzo Aquilanti ◽  
Simonetta Cavalli ◽  
Antonio Aguilar ◽  
Josep M. Lucas
Keyword(s):  
Isotope Effect ◽  
Cross Sections ◽  
Rate Constants ◽  
Kinetic Isotope Effect ◽  
Quantum Calculations ◽  
Kinetic Isotope ◽  
Exact Quantum
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