Preferential binding of the chemical carcinogen N-hydroxy-2-aminofluorene to B-DNA as compared to Z-DNA.

The reaction between the chemical carcinogen N-hydroxy-2-aminofluorene and poly (dG-dC) . poly (dG-dC) (B-form), poly (dG-m5dC) . poly (dG-m5dC) (B-or Z-form), poly(dG-br5dC) . poly (dG-br5dC) (Z-form) has been studied. The carcinogen binds covalently to B-DNA but does not bind significantly to Z-DNA. These results are discussed as related to the accessibility, the electrostatic potential and the dynamic structure of DNA. The accessibility and the electrostatic potential of DNA do not explain the difference in reactivity of the carcinogen since a related carcinogen N-acetoxy-N-acetyl-2-aminofluorene binds equally well to both B and Z-DNA. On the other hand, poly (dG-dC) . poly(dG-dC) and poly (dG-br5dC) . poly(dG-br5dC), in presence of ethidium bromide binds equally well to N-hydroxy-2-aminofluorene. It is suggested that the very low binding of this carcinogen to Z-DNA as compared to B-DNA is due to differences in the dynamic structures of these two forms of DNA.