Formamidopyrimidine-DNA glycosylase (Fpg protein) of Escherichia coliis a DNA repair enzyme that excises oxi-dized purine bases, most notably the mutagenic 7-hydro-8-oxoguanine, from damaged DNA. In order to identify specific contacts between nucleobases of DNA and amino acids from theE. coliFpg protein, photochemical cross-linking was employed using new reactive DNA duplexes containing 5-[4-[3-(trifluoromethyl)-3H-diazirin-3-yl]phe-nyl]-2¢-deoxyuridine dU* residues near the 7-hydro-8-oxoguanosine (oxoG) lesion. .
