Assemblies of brilliant cresyl violet to DNA in the presence of γ-cyclodextrin

The interactions of brilliant cresyl violet (BCV) with herring sperm DNA in γ-cyclodextrin (γ-CD) supramolecular system were studied by UV-vis absorption spectroscopy and cyclic voltammetry (CV). Both UV-vis absorption and CV data show that the interaction of BCV with DNA depends on the concentration ratio of BCV to DNA (R), the initial concentration of BCV and γ-CD. The binding constants of BCV monomer, (BCV)2 dimer and (BCV)2-γ-CD inclusion complex with DNA are 1.64 × 105, 2.56 × 104 and 2.32 × 103 M−1, respectively. It was observed that γ-CD can affect the interactive mode of BCV with DNA. If R is larger than 0.5, the (BCV)2-γ-CD inclusion complex will retain intact and bind to DNA via the electrostatic attraction forces. By contrast, when R is smaller than 0.5, the inclusion complex will be partially dissociated and the free BCV monomer is intercalated into the double-helix structure of DNA attributing to the more favorable microenvironment of DNA for the BCV monomer. Our work postulates the importance of the initial concentration of dye and host molecule on the interaction of dye with DNA in living bodies.