Radiolysis of the Double-Stranded Polynucleotides Poly(A + U) and DNA in the Presence of Oxygen

MICHAELS, H. B., AND HUNT, J. W. Radiolysis of the Double-Stranded Polynucleotides Poly(A + U) and DNA in the Presence of Oxygen. Radiat. Res. 72, 32-47 (1977). The reaction of 02 with -OH adducts produced on poly(A + U) was studied by pulse radiolysis. In the presence of 0O, the absorption spectrum of the poly(A + U) - OH adduct decays to a new spectrum, with a rate constant of 5 X 107 M-1 sec-1. Solutions of poly(A + U) and DNA, in common with other polynucleotides, are sensitive to repetitive pulsing, and in the case of DNA, denaturation takes place and single-stranded regions and pieces are produced. The .OH adduct of native doublestranded DNA does not appear to react with O on a time scale from microseconds to seconds, yet steady-state radiolysis experiments and analysis for peroxides show that DNA hydroperoxides are produced at low doses. The *OH adduct of heat denatured, single-stranded DNA reacts with O as expected. The apparent lack of reaction of double-stranded DNA -OH adducts with 02 is hard to understand, since a reaction with the radiosensitizer NPPN is clearly observable under similar conditions. Possible explanations for the experimental results are discussed.