Studies of eosin Y - DNA interaction using a competitive binding assay.

The interaction between xanthene dye eosin Y and double stranded DNA has been studied by spectrophotometry. The conventional titration study does not show the interaction in the eosin Y - DNA system. Therefore, the competitive binding assay was carried out. The DNA-targeted ligands proflavine and methylene blue were used as competitors. Multivariate curve resolution - alternative least squares method (MCR-ALS) was applied to analyze the spectrophotometric titration data. The experimental binding isotherms were fitted by Scatchard and McGee equations. The binding constant of eosin Y with DNA was found to be 1.7·104 M-1. It is shown that the competitive binding assay requires consideration of heteroassociation for the correct determination of ligand-DNA binding parameters.