Minimized conformational potential energy calculations have been performed for AAF linked to dCpdG at the guanine amino group. This 1s a model for the minor AAF adduct observed in DNA, whose conformational Influence has been difficult to ascertain. A global minimum energy conformation was computed with torsion angles like those of the dCpdG residue of Z-DNA. This conformation was Incorporated into a larger polymer model at a B-Z junction, with the carcinogen residing 1n the groove 1n the Z direction. Local minimum energy conformations of the B type were also computed. In addition, two minima were found with fluorene-cytidine stacking. These results suggest that existing B-Z junctions may be vulnerable to modification by AAF at the guanine amino group, or that such junctions may be Induced by the carcinogen 1f the base sequence 1s appropriate. Otherwise the carcinogen can be located 1n the minor groove of the B helix (5,10,11) or covalently intercalated (13-15).
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