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<span style="mso-bidi-language:HI">Energy barriers and rates of tautomeric transitions in DNA bases: <i>Ab initio </i>quantum chemical study </span>

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Title Energy barriers and rates of tautomeric transitions in DNA bases: Ab initio quantum chemical study
 
Creator Basu, Soumalee
Majumdar, Rabi
Das, Gourab K
Bhattacharyya, Dhananjay
 
Subject Tautomerism
DNA
spontaneous mutation
Quantum chemistry
Transition rate
Unusual base pairing
Intrinsic reaction coordinate analysis
 
Description 378-385
Tautomeric transitions of DNA bases are proton
transfer reactions, which are important in biology. These reactions are involved
in spontaneous point mutations of the genetic material. In the present study,
intrinsic reaction coordinates (IRC)

analyses through ab initio quantum chemical
calculations have been carried out for the individual D A bases A, T, G, C and
also A:T and G:C base pairs to estimate the kinetic and thermodynamic barriers
using MP2/6-31G** method for tautomeric transitions. Relatively higher values
of kinetic barriers (about 50-60 kcal/mol) have been observed for the single bases,
indicating that tautomeric alterations of isolated single bases are quite
unlikely. On the other hand, relatively lower values of the kinetic barriers
(about 20-25 kcal/mol) for the DNA base pairs A:T and G:C clearly suggest that
the tautomeric shifts are much more favorable in DNA base pairs than in
isolated single bases. The unusual base pairing A':C, T':G, C':A or G':T in the
daughter DNA molecule, resulting from a parent DNA molecule with tautomeric
shifts, is found to be stable enough to result in a mutation. The transition
rate constants for the single DNA bases in addition to the base pairs are also

calculated by computing the free energy
differences between the transition states and the reactants.
 
Date 2015-01-16T11:43:29Z
2015-01-16T11:43:29Z
2005-12
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/30390
 
Language en_US
 
Relation C07H21/04
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.42(6) [December 2005]