[Interaction of synthetic ligands containing N,4-disubstituted mono- and diphthalimides with DNA]

Nevel synthetic DNA binding ligands containing N,4-disubstituted mono- and diphthalimide fragments and carrying positively charged groups at both ends of the molecules were characterized by various physiochemical methods. All the ligands were shown to have fluorescence maximum at about 460 nm for excitation at 340 nm. Interaction of these compounds with DNA and synthetic polydeoxyribonucleotides was studied using spectrophotometry, CD and fluorescence measurements. It was shown, that the ligand containing phthalimide fragment connected by flexible chain to dipyrrolcarboxamide fragment, binds to DNA narrow groove covering 5 base pairs. This type of complex formation was found to be followed by increasing of CD band at 280 nm and increasing in fluorescence intensity. If the ligand backbone contains only phthalimide fragments there is no binding in the DNA narrow groove. In this case the weakly fluorescent outside binding type complex is formed, which is characterized by the binding of one ligand molecule with two base pairs.