A Dose-response Study on Opening of Imidazole Ring of Adenine in DNA by Ionizing Radiation

Summary

A dose–response relationship between γ-irradiation and the cleavage of the imidazole ring of adenine in DNA to form formamidopyrimidine has been demonstrated. When the DNA aqueous solution was irradiated with 0·1 Gy under N₂O, there is little evidence of imidazole ring cleavage. A significant increase in cleavage begins to be noticed above 1 Gy reaching a plateau at 1000 Gy. No formamidopyrimidine was formed when 2′-deoxyadenosine was irradiated with up to 1000 Gy. A dose of 100 Gy converts 18 per cent of adenine in DNA to formamidopyrimidine. In irradiated DNA aqueous solution 1000 Gy convert 25 per cent of adenine to formamidopyrimidine under N₂O. Some of the adenine was converted to 7,8-dihydro-8-oxoadenine but in amount that is 20 per cent of that converted to formamidopyrimidine under N₂O. There was more adenine in DNA converted to formamidopyrimidine under N₂O than under N₂.

• 2′-deoxyadenosine aqueous solutions
• DNA aqueous solutions
• formamidopyrimidine
• 7,8-dihydro-8-oxoadenine