Radiation Damage of Purines and Pyrimidines

Purine and pyrimidine bases and their nucleotides with the different number of phos-phoric acid residues were seperated from the aqueous solution of ATP, GTP, CTP and UTP with Dowex-l-formate column. Utilizing this preparation, the above four triphosphate nucleotide solutions were irradiated with 2>:105R gamma rays and then the degree of their irradiation damage was investigated. With respect to the radiosensitivity, it was found that the compounds were resistant to gamma irradiation in the order of adenine, guanine, cytosine and uracil compounds. This may be due to the number of hydroxyl groups of the molecule of compounds studied. The fact that purines were more radio-resistant than pyrimidines may be due to the difference of molecular weight. Futher, in purine nucleotides the radioresistancy was proportional to the number of their phosphoric acid residues