Cu(II)-dependent degradation of DNA by riboflavin

Riboflavin, in the presence of Cu(II), caused breakage of calf thymus DNA and supercoiled pBR322 plasmid DNA. The rate of such DNA degradation was several times greater than that caused by riboflavin alone. The reaction was inhibited under anaerobic conditions, but oxygen could be replaced by the addition of H2O2. Riboflavin reduced Cu(II) to Cu(I), which was shown by using the Cu(I)-sequestering reagent neocuproine, to be an essential intermediate in the DNA degradation reaction. Results obtained with scavengers of active oxygen species and their production by riboflavin and Cu(II) indicated that the species predominantly responsible for DNA breakage is singlet oxygen.