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You are here: Home People Dr. Michael Hutter Abstract - M.Hutter, T.Clark JACS 118 (1996) 7574

Abstract - M.Hutter, T.Clark JACS 118 (1996) 7574

On the Enhanced Stability of the Guanine-Cytosine Base-Pair Radical Cation


Michael Hutter, Timothy Clark*
Computer Chemie Centrum, Uni Erlangen-Nürnberg, Nägelsbachstr. 25, D-91052 Erlangen, Germany

EMail: Michael.Hutter@mpibp-frankfurt.mpg.de

Published in: J. Am. Chem. Soc. 118 (1996) 7574-7577.

Keywords: oxidized DNA, base-pairs, ionization potential, radical cation, density functional theory


Abstract:

Ab initio (UHF/6-31G*) and density functional (Becke3LYP/D95*) calculations have been used to investigate the structures and stabilities of the radical cations of the DNA bases and base pairs. The calculated structures of the base pairs show excellent agreemnet with crystallographic data. The most easily oxidizable base, guanine forms a particularly stable radical cation base pair with cytosine, so that the calculated adiabatic ionization potential for the guanine-cytosine hydrogen bonded complex is about 0.75 eV lower than of guanine itself. UBecke3LYP/D95*//UHF/6-31G* calculations show that the shift of the central hydrogen-bonded proton at N1 of guanine to N3 of cytosine is only slightly endothermic (+1.6 kcal/mol). The product of the corresponding proton shift in the adenine-thymine system is unfavourable by +14.1 kcal/mol. The results suggest that the guanine-cytosine radical cation represents even more a thermodynamic sink in oxidized DNA than might be concluded from the ionization potentials of the individual bases, and that it enjoys about 7.3 kcal/mol extra stabilization from the central low-barrier hydrogen bond.
Michael Hutter, September 1996
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