INTERACTION OF A FURANCARBOXAMIDE ANALOG OF ANTIBIOTIC DISTAMYCIN-A WITH DNA

Flow linear dichroism and circular dichroism were used to examine the interaction with DNA of a isosteric analog of antibiotic distamycin A (Dst) containing three consecutive furancarboxamide fragments in its c entral part (FDst). LD spectra were analyzed using theoretical calcula tions of amplitudes and orientations of the optical transition moments for Dst and FDst. Three types of FDst-DNA complex were revealed, exhi biting ligand to basepair stoichiometry of 1:5, 4:5, and 3:1. The 1:5 complex was analogous to the known monomeric Dst-DNA complex, but was much less stable against ionic strength. The 3:1 complex persisted up to 2 M NaCl. The differences in Dst and FDst binding testify to the su bstantial role of the partial charge on the atoms of ligand facing int o the DNA minor groove.