Theoretical study on the multi-channel reaction of OH radical with 5-methylcytosine

All the possible addition and hydrogen abstraction reactions of OH radical with 5-methylcytosine (5-MeC) have been investigated at B3LYP/6-31++G(d,p)//B3LYP/6-31G(d,p)+ZPE level. The results indicate that OH radical may form complexes with 5-MeC, and the reaction is assumed to occur from these complexes. The estimated activation energies corresponding to addition reactions at N3, C4, C5 and C6 sites of the 5-MeC are 80.96, 63.41, 0.00 and 0.30 kJ/mol, respectively. The order of stability of adducts is P4(C6) > P3(C5) > P2(C4) > P1(N3). The activation energies corresponding to the H9, H10, H11, and H14 abstraction reactions from the 5-MeC are all small, and the stabilization of the products is P8(H14) > P6(H10) > P5(H9) > P7(H11).