Energy contribution of the solvent to the charge migration in DNA

The authors have investigated the interactions of the reaction centers, participating in the charge transfer reaction within the DNA molecule with the phosphate backbones and the solvent molecules, and have estimated the contribution of these interactions into the charge migration in DNA. They have determined the unequal shift of the energy surfaces of the initial and final transition states of the transfer reaction along the energy axis and the dependence of the magnitude of the energy shift on the nature of the reaction centers and the surrounding environment. The nonuniform distribution of the negative charge in the DNA phosphate backbones results in an increase of the positive shift of the energy surface of the DNA base pairs in the center of the structure, where the maximum density of the negative charge is concentrated. Localization of the positive charge on the guanine and the adenine in the DNA base pairs in the oxidized state results in a dependence of the free energy of reaction in the solvent on the pair sequences and their arrangement in the DNA chain. As an example, for the G-C/A-T configuration the positive charges are localized on the same strand that results in a decrease of the free energy of reaction in the solvent for charge migration from G-C to A-T pair by 0.125 eV.