1H NMR study of self-association and restricted internal rotation of the C8-substituted deoxyguanosine 5'-monophosphate adduct of the carcinogen 2-(acetylamino)fluorene.

The high-field 1H NMR spectra of a nucleotide-carcinogen adduct formed from 2-(acetylamino)fluorene (8-(N-fluoren-2-ylacetamido)-2'-deoxyguanosine 5'-monophosphate) have been examined in aqueous solution as a function of concentration at high and low temperatures. An anomalous concentration dependence of NMR spectra was observed at concentration levels over 1 mM. These spectral characteristics have been analyzed in terms of changes in self-association and in the interconversions between torsional diastereomers associated with the central nitrogen. Association constants have been computed. Stacking interactions, which involve both the fluorene and guanine rings, are strong, cooperative and highly temperature-dependent. Deacetylation alters the mode of stacking. Several effects of solvent and aggregation on the conformation at the central nitrogen are discussed.