Conformation change of DNA induced by 6-oxybenzo[a]pyrene radical

The interaction of 6-oxybenzo[a]pyrene radical with DNA in 50% methanol solution was studied in order to determine whether the radical molecule influences DNA conformation. The mode of the interaction of 6-oxybenzo[a]pyrene radical with DNA differed from that of other benzo[a]pyrene derivatives such as 6-hydroxybenzo[a]pyrene, diol-epoxides, etc. The physical binding of the radical molecule to DNA seemed to be transient. This physical binding is most likely due to adsorption at the external surface of DNA, i.e., simply contact in character. It is likely that the local base-pairs are tilted by the contact due to hydrophobic interactions. Furthermore, it is concluded that the covalently bound radical molecule, which is mainly introduced on guanine base, induces a twist of the base plane with respect to other base planes.