© 1984 Oxford University Press
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Sequence specific binding of tetraols of benzo[a]pyrene-diol-epoxide to DNA in neutral and acidic solutions
Department of Chemistry, Tennessee State University Nashville, TN 37203, USA
Comparative binding studies of tetraols (anti-BPTs) derived from trans-7, 8-dihydroxy-anti-9, 10-epoxy-7, 8, 9, 10-tetrahydrobenzo[a]pyrene (anti-BPDE) with native DNA in neutral and acidic solutions reveal that 4–5 times stronger intercalative binding occurs in the protonated duplex DNA than in the unprotonated one. Spectroscopic (absorption and circular dichroism) investigations with synthetic polynucleotides indicate that in neutral pH, anti-BPTs intercalate significantly in poly(dA-dT): poly(dA-dT), only slightly in guanine containing alternating polynucleotides poly(dG-dC): poly(dG-dC) and poly(dA-dC): poly(dG-dT), and hardly in homopolymers poly(dG): poly(dC) and poly(dA): poly(dT). In acidic solutions, on the other hand, all three alternating polynucleotides, poly(dG-dC): poly(dG-dC) in particular, exhibit strong intercalative binding to anti-BPTs although the homopolymers still lack such capability. These results are very similar to those of corresponding pyrene studies suggesting that pyrene can be a useful model compound for the DNA binding studies of benzo[a]pyrene metabolites. The observed enhanced binding of anti-BPTs in the acidic natural DNA solution is seen as the consequence of changes in base sequence preference upon base protonation.