Abstract
The genome is continuously exposed to a variety of harmful factors that result in a significant amount of DNA damage. This article examines the influence of a multi-damage site containing oxidized imino-allantoin ((OX)Ia) and 7,8-dihydro-8-oxo-2'-deoxyguanosine ((OXO)dG) on the spatial geometry, electronic properties, and ds-DNA charge transfer. The ground stage of a d[A(1)(OX)Ia(2)A(3)(OXO)G(4)A(5)]*d[T(5)C(4)T(3)C(2)T(1)] structure was obtained at the M06-2X/6-D95**//M06-2X/sto-3G level of theory in the condensed phase, with the energies obtained at the M06-2X/6-31++G** level. The non-equilibrated and equilibrated solvent-solute interactions were also considered. Theoretical studies reveal that the radical cation prefers to settle on the (OXO)G moiety, irrespective of the presence of (OX)Ia in a ds-oligo. The lowest vertical and adiabatic ionization potential values were found for the (OXO)G:::C base pair (5.94 and 5.52 [eV], respectively). Conversely, the highest vertical and adiabatic electron affinity was assigned for (OX)IaC as follows: 3.15 and 3.49 [eV]. The charge transfers were analyzed according to Marcus' theory. The highest value of charge transfer rate constant for hole and excess electron migration was found for the process towards the (OXO)GC moiety. Surprisingly, the values obtained for the driving force and activation energy of electro-transfer towards (OX)Ia(2)C(4) located this process in the Marcus inverted region, which is thermodynamically unfavorable. Therefore, the presence of (OX)Ia can slow down the recognition and removal processes of other DNA lesions. However, with regard to anticancer therapy (radio/chemo), the presence of (OX)Ia in the structure of clustered DNA damage can result in improved cancer treatment outcomes.