Binding geometry of benzo[a] pyrene diol epoxide covalently bound to DNA. A flow linear dichroism study

Flow linear dichroism (LD) provides new structural information on 7β,8α-dihydroxy-9α, 10α-epoxy-7,8,9,10-tetrahydrobenzo[a] pyrene (anti-BPDE) covalently bound to DNA: by resolving the LD spectrum with respect to the polarized absorption components of the pyrenyl chromophore, we have determined the orientations of the in-plane symmetry axes of the bound compound relative to the helix axis of DNA [they are on average oriented at 70°(short axis) and 30°(long axis)]; for both (+)- and (–)-anti-BPDE adducts the flexibility of the DNA is increased