Two major products (adducts A and B) from the reaction of 2'-deoxyguanosine (dGuo) with13-hydroperoxylinoleic acid were detected by liquid chromatography/mass spectrometry (LC/MS). Adducts A and B were also the major products formed enzymatically when dGuo wasincubated in the presence of linoleic acid and lipoxygenase. The mass spectral fragmentationpatterns of adducts A and B suggested that unique modifications to the nucleoside had beenintroduced. This resulted in the characterization of a novel bifunctional electrophile, 4-oxo-2-nonenal, as the principal breakdown product of linoleic acid hydroperoxide. In subsequentstudies, adduct A was found to be a substituted ethano dGuo adduct that was a mixture ofthree isomers (A
1-A
3) that all decomposed to form adduct B. Adduct A
1 was the hemiacetalform of 3-(2'-deoxy-
-
D-erythropentafuranosyl)-3,5,6,7-tetrahydro-6-hydroxy-7-(heptane-2' '-one)-9
H-imidazo[1,2-
]purine-9-one. Adducts A
2 and A
3 were the diastereomers of the open chainketone form. Adduct B was the substituted etheno dGuo adduct, 3-(2'-deoxy-
-
D-erythropentafuranosyl)imidazo-7-(heptane-2' '-one)-9-hydroxy[1,2-
]purine, the dehydration product ofadducts A
1-A
3. Identical covalent modifications to dGuo were observed when calf-thymus DNAwas treated with 4-oxo-2-nonenal. These data illustrate the diversity of reactive electrophilesproduced from the peroxidative decomposition of lipids and have implications in fully assessingthe role of lipid peroxidation in mutagenesis and carcinogenesis.