Identification of guanine-adducts of carcinogens by their fluorescence

A fluorescence technique has been devised to identify guanosine adducts, substituted at the N7, O6 and N2 positions. The technique is based on fluorescence excitation spectra taken under neutral and alkaline conditions. At neutral pH, the N7- and O6- derivatives were fluorescent while at an alkaline pH the N7-derivatives were irreversibly destroyed with the loss of fluorescence. In alkaline solution the O6- and N2-derivatives were fluorescent but neutralization suppressed the fluorescence of the N2- derivatives. The technique was examined using methylmethanesulfonate, known to produce in the main N7- alkylation, and with diethyl sulfate known to produce N7- alkylation and to a lesser extent O6-alkylation. Fluorescence spectra typical of N 2-alkylation, in addition to N7-alkylation was produced by dimethylcarbamoylchloride.