Solution conformation of the (-)-cis-anti-Benzo(a)pyrenyl-dG adduct opposite dC in a DNA duplex: intercalation of the covalently attached BP ring into the helix with base displacement of the modified deoxyguanosine into the major groove

The covalently attached Benzo(a)pyrenyl ring (BP) intercalates between the dC5.dG18 and dC7.dG16 base pairs of the DNA duplex molecule and displaces deoxyguanosine (BP)-dG6 and its partner cytosine dC17 from the helix into the major groove. The benzylic ring in the intercalated BP ring is oriented towards the minor groove in the (+)cis-anti-(BP)dG.dC duplex isomer and towards the major groove in the (-)cis-anti isomer. Both duplex adducts displace the modified deoxyguanosine into the major groove.