Reactions of malonaldehyde and acetaldehyde with calf thymus DNA: formation of conjugate adducts

Our previous work has shown that treatment of nucleosides with malonaldehyde simultaneously with acetaldehyde affords stable conjugate adducts. In the present study we demonstrate that conjugate adducts are also formed in calf thymus DNA when incubated with the aldehydes. The adducts were identified in the DNA hydrolysates by their positive ion electrospray MS/MS spectra, by coelution with the 2'-deoxynucleoside standards, and, in the case of adducts exhibiting fluorescent properties, also by LC using a fluorescence detector. In the hydrolysates of double-stranded DNA (ds DNA), two deoxyguanosine and two deoxyadenosine conjugate adducts were detected and in single-stranded DNA (ss DNA) also, the deoxycytidine conjugate adduct was observed. The guanine base was the major target for the malonaldehyde-acetaldehyde conjugates and 2'-deoxyguanosine adducts were produced in ds DNA at levels of 100-500 adducts/10(5) nucleotides (0.7-3 nmol/mg DNA).