Circular dichroism and proton magnetic resonance studies of dApdG modified with 2-aminofluorene and 2-acetyl-aminofluorene

The conformational properties of 2'-deoxyadenylyl-(3'-5')-2'-deoxyguanosine (dApdG) modified by the covalent binding of the carcinogens 2-acetylaminofluorene (AAF) and 2-aminofluorene (AF) have been investigated, utilizing circular dichroism and proton magnetic resonance spectroscopy. The attachment of AF residues to the C-8 position of guanosine introduced smaller changes in the circular dichroism spectra of dApdG than the binding of AAF residues. Similarly, binding of AF residues caused lower up-field shifts for the H-2 and H-8 protons of adenine than the AAF residues. These results suggest that AF residues are less stacked with the neighboring A base in dApdG than AAF. Thus, AF residues bound on the C-8 position of guanine might induce less distortion in conformation of the modified regions than AAF residues.