Laser spectroscopic studies of DNA adduct structure types from enantiomeric diol epoxides of benzo[a]pyrene.

A methodology based on 77 K laser-excited fluorescence spectroscopy, fluorescence quenching, and fluorescence line narrowing is shown to be a highly selective and sensitive approach for the study of polycyclic aromatic carcinogen-DNA complexes. Three and five different DNA adducts derived from (+)-trans-7,8-dihydroxy-anti-9,10-epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene and its (-)-enantiomer are identified, respectively. Two different methods are used to classify the adducts as type I (interior) or type II (exterior), and both yield consistent results. The first high-resolution fluorescence excitation spectra are reported for DNA adducts. These spectra are suggested to be useful for characterizing the strength of the interaction between the fluorescent chromophores and the DNA bases. The above methodology has the potential for monitoring the fates of different adducts as a function of time in repair-competent cells.