Reactivity and binding of benzo(a)pyrene diol epoxide to poly(dG-dC)·(dG-dC) and poly(dG-m5dC)·(dg-m5dC) in the B and Z forms

Khadija Moussaoui, Nicholas E. Geacintov, Ronald G. Harvey

Research output: Contribution to journalArticlepeer-review


The physical and covalent binding of the carcinogen benzo (a)pyrene-7,8-diol-9,10-oxide (BaPDE) to poly(dG-dC)·(dG-dC) and poly(dG-m5dC)·s(dG-m5dC) in the B and Z forms were studied utilizing absorbance, fluorescence and linear dichroism techniques. In the case of poly(dG-dC)·(dG-dC) the decrease in the covalent binding of BaPDE with increasing NaCl concentration (0.1-4 M) as the B form is transformed to the Z form is attributed to the effects of high ionic strengths on the reactivity and physical binding of BaPDE to the polynucleotides; these effects tend to obscure differences in reactivities with the B and Z forms of the nucleic acids. In the case of poly(dG-m5dC)·(dG-m5dC) the B-to-Z transition is induced at low ionic strength (2 mM NaCl + 10 μM Co(NH3)6Cl 3) and the covalent binding is found to be 2-3-times lower to the Z form than to the B form. Physical binding of BaPDE by intercalation, which precedes the covalent binding reaction, is significantly lower in the Z form than in the B form, thus accounting, in part, for the lower covalent binding. The linear dichroism characteristics of BaPDE covalently bound to the Z and B forms of poly(dG-m5dC)·(dG-m5dC) are consistent with nonintercalative, probably external conformations of the aromatic pyrenyl residues.

Original languageEnglish (US)
Pages (from-to)285-297
Number of pages13
JournalBiophysical Chemistry
Issue number4
StatePublished - Oct 1985


  • Benzo(a)pyrene-7,8-diol-9,10-epoxide
  • Linear dichroism
  • Poly(dG-dC)·(dG-dC)
  • Poly(dG-mdC)·(dG-mdC)

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Organic Chemistry


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