Comparative studies on the 7-iodo and 7-fluoro derivatives of N-acetoxy-N-2-acetylaminofluorene: binding sites on DNA and conformational change of modified deoxytrinucleotides

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Abstract
GMP and native chicken erythrocyte DNA were reacted with 7-iodo and 7-fluoro derivatives [AAIF and AAFF] of N-acetoxy-N-2-acetylaminofluorene. The 7-halogeno derivatives react on C-8 of guanine. The respective amount of arylamidation (covalent linkage on the C-8 of guanine [G]) and arylation (covalent linkage on 2-NH2 groups of C3 of G) addition products was determined in native and denatured DNA-[14C]AAIF. Two G containing deoxytrinucleotides modified by the carcinogens AAFF or AAIF were studied comparatively by circular dichroism, and as a function of several parameters known to affect the conformation of the deoxytrinucleotides. The induced optical activity in the fluorofluorene ring seemed to be sensitive to the conformational changes of the deoxytrinucleotides. AAIF residue exhibited lower induced optical activity which remained unchanged when the deoxytrinucleotide conformation was affected. AAFF and AAIF modified deoxytrinucleotides adopt a conformation which nicely fits with the insertion-denaturation and outside-binding model, respectively.