Binding mode of distamycin to d(CGTACGTACG)(2) in the 2:1 solution complex as determined by two-dimensional H-1 NMR and molecular modelling studies

Previous UV and CD studies indicated a high affinity of d(CGTACGTACG)(2), 1, for distamycin, 2, though it does not possess the commonly accepted site for this ligand. The binding mode of the drug has now been investigated by a combination of high-resolution H-1 NMR and molecular modelling. The structure of the complex contains two molecules of drug symmetrically placed at the centre along the strands of DNA, spanning the minor groove with the first two pyrrole rings of one molecule in close contact with those of the other one.