Detection and structural characterization of amino polyaromatic hydrocarbon-deoxynucleoside adducts using fast atom bombardment and tandem mass spectrometry

Fast atom bombardment (FAB) and tandem mass spectrometry (MS/MS) are shown to be useful methods for the detection and structural characterization of nanogram amounts of amino polyaromatic hydrocarbon-nucleoside DNA adducts. The positive ion spectra of four aromatic amine guanosine adducts were studied in detail. The FAB spectra of these adducts exhibit an [MH]+ ion and a more abundant aglycon fragment ion, [AH2]+, which results from the loss of the deoxyribose sugar. The sensitivity of the adducts to FAB was enhanced by preparing trimethylsilyl (TMS) ether derivatives. High-quality full-scan spectra could be obtained on less than 70 ng of the derivatized adducts without signal averaging. With a B/E-linked scan of the [MH]+ ion for the TMS2 species, these same adducts could be detected by examination of their metastable ion spectra at levels as low as 4-5 ng (S/N greater than 10). Collision-induced dissociation (CID) of the [MH]+ ion yields the aglycon fragment and an ion, S1, which results from cleavage through the sugar. The CID spectrum of the aglycon [AH2]+ ion is much more useful, providing structural information relating to the base, the polyaromatic hydrocarbon, and, possibly, the site of covalent attachment. Differentiation of isomeric aminophenanthrene-guanine adducts was demonstrated on the basis of the CID spectra of their respective [AH2]+ ions. The use of TMS derivatives also improves the sensitivity of these methods.