A molecular orbital analysis of the DNA bases

The carcinogen-DNA interaction can be described as an electron transfer fro m the DNA (HOMO) to the carcinogen (LUMO). To get a description of the DNA' s HOMO, the 35 tautomers of the DNA bases are analyzed. Koopmans' (ROHF and OVGF) and Delta SCF vertical/adiabatic AM1 ionization potentials combined with other calculated electronic properties provide additional insight on t he stability and relative population of the tautomers. It is correctly foun d that the one-electron transfer and the electrophilic attack occurs prefer entially at C6 and N7 of guanine. (C) 1999 Elsevier Science B.V. All rights reserved.