Scheme 1.
Schematic representation of prototropic equilibria in the one-electron oxidized G:C. The intra-base pair proton transfer within the one-electron oxidized G:C (process 1) and proton transfer to water either from the N1 atom (process 2) or from the nitrogen atom in the exocyclic amine (N2) of the guanine moiety in the one-electron oxidized G:C (process 4) are shown. The interconversion between G(N1-H)•:C and G(N2-H)•:C is represented by process 3. The conformation of the G(N1-H)•:C shown in this scheme has been adopted from the gas phase optimized geometry obtained by Bera et al. by using DFT (see ref. 25 for details) and this conformation of G(N1-H)•:C has been verified in this work for hydrated one-electron oxidized G:C.