Studies of the binding of diolepoxide metabolites of polycyclic aromatic hydrocarbons to DNA using electrofluorescence polarization spectroscopy.

In the electrofluorescence method, a solution of DNA with covalently bound polycyclic hydrocarbons is placed in an electric field, and changes in the intensity of polarized fluorescence are observed. Under the correct conditions, these charges can be used to determine a value for the angle psi between the long axis of the hydrocarbon molecule and the axis of the DNA helix. For DNA or poly(dA-dT) treated with each stereoisomer of anti-benzo[c]phenanthrene diolepoxide, psi ranged from 55 degrees to 61 degrees, consistent with a mixture of quasi-intercalated adenine adducts and externally bound guanine adducts. Similar results were obtained with another set of 'fjord-region' diolepoxides, derived from benzo[c]chrysene. Adducts in DNA treated with diolepoxides derived from chrysene, 5-methylchrysene or 6-methylchrysene gave psi of about 53 degrees, so the predominant adducts are externally bound, probably in the minor groove of DNA.