Radiation chemistry of 2'-deoxycytidylyl-(3'-5')-2'-deoxyguanosine and its sequence isomer in N2O- and O2-saturated solutions.

The radiation chemistry of the dinucleoside monophosphate d(CpG) and its sequence isomer, d(GpC), has been examined in aqueous solutions saturated with either N2O or O2. The products were isolated using HPLC, and the major products were identified using proton NMR spectroscopy and mass spectrometry. The major products include 5,6-dihydroxy-5,6-dihydrouracil (glycol) derivatives, 5- and 6-hydroxycytosine substitution products, 1-carbamoyl-2-oxo-4,5-dihydroxyimidazolidine products, and the 8-hydroxyguanine substitution product. Both trans stereoisomers of the imidazolidine derivatives are obtained from d(CpG) as well as from its sequence isomer. These are prominent products when the irradiation is carried out in the presence of oxygen, but they are not observed in the absence of oxygen.