Fluorescence line narrowing-nonphotochemical hole burning spectrometry: femtomole detection and high selectivity for intact DNA-PAH adducts.

A new fluorescence line narrowing (FLN) apparatus is described and evaluated through experiments on intact DNA-PAH (polycyclic aromatic hydrocarbon) and globin-PAH adducts, as well as polar PAH metabolites. A detection limit of approximately 3 modified bases in 10(8) for a DNA adduct formed with a diol-epoxide of benzo[a]pyrene (BPDE-DNA) is reported for 20 micrograms of DNA at a spectral resolution of approximately 8 cm-1. The methodology employed avoids or minimizes spectral degradation and loss of sensitivity due to photooxidation and nonphotochemical hole burning (NPHB). A new double selection technique that employs both FLN and NPHB is described and found to lead to a significant improvement in selectivity over that obtained with conventional FLN.