2‘-Deoxyguanosine (DG) Oxidation and Strand-Break Formation in DNA by the Radicals Released in the Photolysis of N-tert-Butoxy-2-pyridone. Are tert-Butoxyl or Methyl Radicals Responsible for the Photooxidative Damage in Aqueous Media?

[reaction: see text] The photolysis of pyridone 3b (photo-Fenton reagent) in benzene releases tert-butoxyl radicals, which have been trapped by DMPO and EPR-spectrally identified. In aqueous solution, however, the fragmentation of the tert-butoxyl into methyl radicals prevails and the former radicals are of no direct consequence in the photooxidation of 2'-deoxyguanosine (dG) and pBR 322 DNA. The photooxidative damage of nucleic acids is caused by the oxyl radical species generated from the methyl radicals with oxygen.