This study demonstrates that the reaction of Fe(II)-EDTA
and hydrogen peroxide with the single-stranded nucleic
acids d(pT)70 and a 29 base sequence containing a mixture
of bases results in substantial damage which is not
directly detected by gel electrophoresis. Cleavage
of the DNA sugar backbone is enhanced significantly
after the samples are incubated at 90 oC in the presence
of piperidine. The latter reaction is used in traditional
Maxam-Gilbert DNA sequencing to detect base damage,
and the current results are consistent with reaction
of the hydroxyl radical with the bases in single stranded
DNA (although reaction with sugar may also produce
adducts which are uncleaved, but labile to cleavage
by piperidine). We propose that hydroxyl radicals
may react preferentially with the nucleic acid bases
in ssDNA and that reaction of the sugars in dsDNA is
dominant because the bases are sequestered within the
double helix. These results have implications both
for the study of single-stranded DNA binding protein
binding sites and for the interpretation of experiments
using the hydroxyl radical to probe DNA structure or
to footprint double-stranded DNA binding protein binding
sites.Return to publication list
