Radical damage to
DNA has been implicated in cell death, cellular dysfunction, and
cancer. A recently developed method for detecting
DNA radicals uses the nitrone spin trap DMPO (5,5-dimethyl-1-pyrroline N-oxide) to trap radicals. The trapped radicals then decay into stable nitrone adducts detectable with anti-DMPO
antibodies and quantifiable by ELISA or dot-blot assay. However, the sequences of
DNA that are damaged are likely to be as important as the total level of damage. Therefore, we have developed immunoblotting methods for detection of
DNA nitrone adducts on electrophoretically separated
DNA, comparable to Western blotting for
proteins. These new techniques not only allow the assessment of relative radical adduct levels, but can reveal specific
DNA fragments, and ultimately
nucleotides, as radical targets. Moreover, we have determined that denaturation of samples into
single-stranded DNA enhances the detection of
DNA-DMPO adducts in our new blotting methods and also in ELISA.