Chain Scission and Hydrogen Bond Breakage on Irradiation of DNA

Abstract

Numerous investigators, including the authors, have shown that exposure of deoxyribonucleic acid (DNA) to ionizing radiation results in chemical changes of various types. These changes include breakage of internucleotide linkages (1-4), breakage of hydrogen bonds (4-7), destruction of bases (4, 8, 9), cross-linking of polynucleotide chains (1, 3, 10), and other reactions (1, 4, 5). In the present study, a quantitative estimation of the breakage of internucleotide links has been made by determining the rate of attack of phosphomonoesterase on irradiated DNA. The changes in ultraviolet absorption of DNA have been used to estimate the breakage of hydrogen bonds and the destruction of total bases. Finally, the G values for various radiation-induced reactions of DNA have been compiled, and the radiobiological implications discussed.