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 p hosphate under N2 and air caused the same loss. Under N2O this loss wa s doubled showing that the reactions of OH radicals mainly lead to str and breakage. The stability of the double helix is decisive for the yi eld of double strand breaks. In this work the radiation-induced degrad ation was altered by different sodium phosphate concentration, by subs tituting phosphate for perchlorate and by changing the temperature in the radiolysis of DNA under air. A decrease of the strength of non-cov alent 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.