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RESEARCH PRODUCT

Studies on Adduct Formation of (+)-Anti-Benzo[a]pyrene 7,8-Dihydrodiol 9,10-Epoxide with the oligonucleotides 5′-d(CCTATCGTTATCC) and 5′-d(CCTATm5CGTTATCC)

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Abstract Adduct formation of (+)-anti-benzo[a]pyrene 7,8-dihydrodiol 9,10-epoxide [BPDE] and 5′-d(CCTATCGTTATCC) or 5′-d(CCTATm5CGTTATCC) (G = binding target) has been studied. The extent of trans-BPDE-N2-dG adduct formation was higher in the oligonucleotide with 5′-d(m5CG) sequence context in both single- and double stranded form compared to the non-methylated analogue. The stimulating effect of m5dC on adduct formation has previously been demonstrated in other experimental systems. The increase in yield could possibly be rationalized in terms of prestacking of the pyrenyl ring with the nucleobases prior to the nucleophilic addition. In the present study, both UV absorption and induced circular dichroism of the trans-BPDE-N2-dG adduct in the m5dC-containing duplex indicate substantial adduct heterogeneity and are consistent with the presence of both external localized complexes and those with intercalative binding characteristics.