[Interaction of rubomycin and its aglycone with DNA studied by fluorescent methods]

The fluorescent characteristics of rubomycin as dependent on the environmental conditions (different solvents, acidity of the medium, ionic strength) were studied. A model explaining suppression of the rubomycin fluorescence on the antibiotic interaction with DNA is described. The model confirmed intercalation and preferable binding with purines as compared to pyrimidines. The constants of rubomycin and aglycone interaction with DNA were determined. The use of the antibiotic concentrations less than 10(-6) M allowed the determination of a higher constant characterizing "strong binding". The nonlinearity of the curve of DNA titration with the antibiotic plotted on the Scatchard coordinates indicates the heterogeneity of the binding sites. The constant of the aglycone binding to DNA was approximately 2 orders lower at the same number of the binding sites in one molecule. The decrease in the constant of rubomycin interaction with DNA of an increased ionic strength and the low constant of the aglycone interaction with DNA as compared to that of the antibiotic itself confirmed the suggestion that there formed a bond between the amino sugar and the phosphate groups.