In living cells, polycyclic aromatic hydrocarbons, a well known class of chemical carcinogens, are metabolically activated to mutagenic and tumorigenic bay-region diol epoxide derivatives. The mechanisms by which these chemicals cause cancer are not well understood. However, there is experimental evidence which indicates that these reactive molecules bind chemically to DNA, and that these lesions somehow give rise to mutations. Subtle differences in the steric orientations of the diol and epoxide groups, as well as other, seemingly small structural variations, can give rise to profound differences in the tumorigenic and mutagenic potentials of these molecules. The specific genomic DNA sequences in which these covalently bound carcinogens are located, may also be of critical importance. The objectives of this work are to characterize the type of DNA damage, and the differences in adduct conformations and surrounding DNA nucleotide sequences, caused by specific pairs of biologically active and inactive, but structurally related pairs of PAH diol epoxide molecules. The approach consists of synthesizing site-specific covalent adducts derived from the binding of these pairs of related PAH diol epoxide molecules to oligodeoxynucleotides of defined base sequence. The characteristics of these modified DNA sequences, and the perturbations of normal base pairing processes caused by the covalently bound polycyclic aromatic residues, will be studied by sensitive physico-chemical, spectroscopic, and biochemical techniques. The existence of carcinogen-base stacking interactions, solvent-exposed adduct conformations, and the formation of kinks, bends, or flexible hinge points at the binding sites will be studied. Carcinogen-modified sequences which can be synthesized in sufficiently high yields, and which have appropriate characteristics for NM studies, will be subjected to one-dimensional and two-dimensional NMR analysis. The long range objectives of this work are to elucidate those features, on a molecular level, which distinguish mutation-prone PAH diol epoxide-DNA lesions derived from biologically highly active molecules, from benign adducts, derived from inactive structurally related PAH diol epoxide derivatives. This knowledge should ultimately lead to a better understanding of the molecular basis of mutagenesis induced by this class of carcinogens and mutagens.
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