Theoretical study on the hydrolytic deamination reaction mechanism of adenine-(H2O)n (n = 1-4)

The hydrolytic deamination reaction mechanism of adenine (A) have been theoretically investigated at the B3LYP/6-31G** level. It is found that the hydrolytic deamination reaction of A may proceed in a stepwise way. The commonly accepted mechanism is that a tetra-coordinated intermediate is formed first by the hydrolysis reaction, followed by the deamination reaction with CN broken and CO formed. The study of the potential energy surface shows that the deamination reaction of A-nH2O (n = 1, 2, 3, 4) does not take place because of a higher barrier for the opening system, which is agreement with the experimental result. While for the closing system, the results show that the deamination reaction of A-nH2O (n = 3, 4) is possible to proceed because one water molecule acts as catalyst and the others act as medium, which may play an important role in mutation of DNA. In addition, the solvent effect has been studied by the PCM model. Our present calculations have rationalized all the possible reaction channels.