Radiolysis of DNA studied by HPL-gel chromatography.

Radiolytic loss of highly polymerized calf thymus DNA was measured by HPL-gel chromatography. Irradiation of DNA in 10(-2) mol dm-3 sodium phosphate under N2 and air caused the same loss. Under N2O this loss was doubled showing that the reactions of OH radicals mainly lead to strand breakage. The stability of the double helix is decisive for the yield of double strand breaks. In this work the radiation-induced degradation was altered by different sodium phosphate concentration, by substituting phosphate for perchlorate and by changing the temperature in the radiolysis of DNA under air. A decrease of the strength of non-covalent bonds in DNA always leads to an increase of degradation of DNA. Radiosensitivity of DNA is higher at pH 7 than at pH 9 or 5.