METHODS OF INVESTIGATION OF THE STRUCTURE AND ACTION MECHANISMS OF ACTIVE SITES OFENZYMES - New Trends in Enzyme Catalysis and Biomimetic Chemical Reactions - page 30

In the framework of this approach, the theoretical magnitude of kinetic isotope effect
is given by:
where MMI, ZPI, and EXP are related to the moment of inertia, zero point energy, and
excited states energy, respectively. The input required for BEBOVA analysis is (1) the
structure of the initial and final states; (2) the substrate spring force constants for each
internal coordinate; (3) the list of atomic masses; and (4) the reaction coordinate.
The method was applied to nucleophilic substitution on including hydrolysis
and ADP-ribolization reactions of peptide substrates. It was shown that in these systems
the hydrolytic TS's follow mechanisms with highly dissociative structure. In the TSs
the ADP-ribosyl bond is completely broken with low but significant bonding to the
water nucleophile.
The analysis of experimental KIEs via the structure interpolation approach to bond
energy/ bond order vibrational analysis (BEBOVA) makes it possible to quantitatively
determine TS's (Berti, 1999 and references therein).
Solvent isotope effects are complicated by the fact that primary, secondary and
medium effects are multiplied together and
In proton inventory technique, solvent isotope effects are plotted against atomic
fractions of deuterium in mixed isotopes of water. A linear plot represents a contribution
from a single origin, whereas nonlinear plots may be generated from multiple origins.