Reorganization, activation and ionization energies for hole transfer reactions through inosine–cytosine, 2-aminopurine – Thymine, adenine–thymine, and guanine–cytosine base pairs: A computational study

Ionization energies of purine and pyrimidine bases and their base pairs are calculated together with the reorganization energies for hole transfer through DNA bases by applying the B3LYP/6-311++G** method. The results suggest that the vertical ionization energy (VIE) is the maximum for inosine–cytosine (IC, 8.02 ev) followed by adenine–thymine (AT, 7.88 ev), 2-aminopurine–thymine (ApT, 7.72 ev) and guanine–cytosine (GC, 7.29 ev) base pairs. The adiabatic ionization energy (AIE) values for IC and AT are the same (7.70 ev) followed by ApT (7.52 ev) and GC (6.92 ev). Among the barrier heights calculated, the GC → AT (or G → A) hole transfer involves the maximum barrier height (0.723 ev) followed by G → I (0.686 ev). The A → A hole transfer involves the smallest barrier (0.106 ev).