A theoretical study of the ground‐state potential surface of guanine and its binding with oxygen and water

A molecular orbital geometry optimization study of the potential surface of guanine, guanineO₂, and guanineO₂water reaction products in the ground state has been carried out. The origin of the asymmetric double‐well potential surface of guanine suggested earlier on the basis of experimental observations has been explained. The most stable binding of O₂ with guanine (G) is found to occur at the C4C5 double bond of the latter molecule. In the case of GO₂water reaction product (HOOGOH), the groups OOH and OH bind at C4 and C8, respectively. The possiblity of a polymeric reaction product of the type R1(GOOG)nR2 (R1, R2 = H, OH) has also been suggested. These results are broadly supported by experimental observations. The mechanism of spectral oscillations observed in UV‐irradiated guanine solutions has been discussed.