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

- Reorganization and activation energies of DNA base pairs calculated.
- Guanine → Adenine hole transfer involves the largest barrier closely followed by Guanine → Inosine barrier.
- Adenine → Adenine hole transfer involves the smallest barrier.
- The inosine-cytosine base pair has the largest and the guanine-cytosine has the smallest ionization energy.

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).

Inosine-cytosine base pair.