RADIOLYSIS OF DNA IN THE PRESENCE OF A PROTEIN STUDIED BY HPL-GEL CHROMATOGRAPHY

The influence of bovine serum albumin (BSA) on the radiolysis of doubl e-stranded DNA was studied by measuring the loss of highly polymerized DNA with HPL-gel chromatography. The scavenger capacity of BSA for OH .-radicals k(BSA) [BSA] was kept constant at 7.8 x 10(5) s(-1), when D NA (0.1 mg/ml) was irradiated under different gas conditions (air, N-2 and N2O), at pH 7 and 5 and with different ionic conditions, The resu lting protein radicals react with DNA producing DNA-protein crosslinks and DNA double-strand breaks. The yield and the kind of DNA damage de pend on the nature of the protein radicals and their association with DNA. High phosphate concentration prevents the association of BSA with DNA and causes a reduction of the protection by BSA against double-st rand breakage of DNA. Radiolysis in the presence of BSA in perchlorate solution leads to more strand breakage and less protein crosslinking than in phosphate solution because perchlorate is more chaotropic than phosphate. Changing the pH from 7 to 5 increases the protection by BS A against DNA strand breakage.