Molecular Pharmacology, Vol 6, 649-658, Copyright © 1970 by the American Society for Pharmacology and Experimental Therapeutics

Competition for Polymeric Binding Sites between Acridine and Triphenylmethane Dyes

¹ Unit of Protozoology, Microbiological Institute, Hebrew University, Jerusalem, Israel
² National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland 20014
³ Department of Chemistry, Faculty of Science, University of Hiroshima, Hiroshima, Japan

Acridine and triphenylmethane dyes are known to display therapeutic interference in combination, but the basis for this interaction is not understood. When added to DNA, representatives of each group of dyes, which alone are optically inactive, displayed strong signals as monitored by optical rotatory dispersion. However, when trypaflavin and crystal violet were both added to the polymer, only the signal due to bound trypaflavin was observed. This competition for the polymer was explored on the one hand by alterations in the concentrations and structures of the dyes, and on the other by the use of different polymers: poly--L-glutamic acid, apurinic acid, and polylysine. It was found that the two amino groups attached to positions 3 and 6 of the acridine ring greatly influenced the competition. For example, 10-methylacridine orange did not abolish the signal of crystal violet in the presence of DNA. The polymer was also influential, so that the competition appeared reversed on poly--L-glutamic acid. Supplementary data obtained from spectroscopy and fluorescence quenching are also presented. These observations are discussed in terms of the biological phenomenon of therapeutic interference.