Interaction of 4-(9-acridinylamino)aniline and derivatives with DNA. Influence of a lysylglycyl side chain on the binding parameters.

N-[4-(9-Acridinylamino)-3-methoxyphenyl]methanesulfonamide, an antitumor drug which has been tested in clinical trials, is known to bind to DNA by the intercalation of its 9-aminoacridine moiety between DNA base pairs and its anilino side chain would then be located in the narrow groove. The intercalatice binding of the drug has been studied here, using ESR through competition with a spin-labelled 9-aminoacridine. In addition the affinity parameters of the parent compound 4-(9-acridinylamino)aniline and a new peptidic derivative, 4-(9-acridinylamino)-N-(lysylglycyl)aniline, have been evaluated by the same technique. Thus the influence of the side chains structures on the dissociation constant values was determined. The results reported here suggest that the affinity of this drug to DNA could be increased by the introduction of a lysyl residue.