Effects of Ionizing Radiation on Aqueous Solutions of Inosine and Adenosine

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Abstract
When aqueous solutions of inosine, adenosine, guanosine, and xanthosine are irradiated with 15-Mev electrons in the absence of oxygen, the main reaction is opening of the imidazole ring to form the corresponding foramidopyrimidine. The sugar moiety is attacked to a lesser extent and is followed by release of free base. When oxygen is present during irradiation the amount of nucleoside destroyed is 2-3 times as great as in the absence of oxygen. The increased destruction is due almost entirely to an increased base attack. After irradiation in the presence of oxygen no UV-absorbing product arising from base attack is found, and the reaction in oxygen seems to be qualitatively different from the reaction in the absence of oxygen. These reactions are not confined to nucleosides but occur with nucleotides and at least one base, adenine. It is suggested that, if a radiobiological change is enhanced by the presence of oxygen during irradiation and is also produced by an alkylating agent, then attack on the guanine moiety may be the initial chemical lesion.