Reactions of dihydrodiol epoxides of 5-methylchrysene and 5,6-dimethylchrysene with DNA and deoxyribonucleotides

Both syn and anti dihydrodiol epoxides from 5-methylchrysene (5-MCDE) and 5 ,6-dimethylchrysene (5,6-DMCDE) were reacted under the same conditions with native DNA, denatured DNA, and purine deoxyribonucleotides, and the produc ts were quantified. The extents of reaction with the deoxyribonucleotides w ere consistently greater for 5,6-DMCDE than for 5-MCDE. The yield of adduct s in the reaction with DNA ranged from being a few-fold to 50-fold greater than those found in the corresponding deoxyribonucleotide reactions for bot h 6-MCDE and 5,6-DMCDE. The DNA-dependent enhancement of product yield was greater for 5-MCDE than for 5,6-DMCDE with a few exceptions among cis and t rans deoxyadenosine adducts. The most substantial differences in DNA-depend ent enhancement were found for deoxyguanosine adducts; thus, steric hindran ce between the B-methyl group in the 5,6-DMCDE and the minor groove in the DNA double helix may account for the greater DNA-dependent enhancement foun d in the 5-MCDE reactions.