In this paper, all of the studies were carried out under the condition of physiological pH. The interaction between Congo red and DNA was studied by spectroscopic, electrochemical, thermodynamic and viscometry methods, using Nature red as molecular probe. Binding stoichoimetry, binding constant and the corresponding thermodynamic parameters were obtained. The results indicated that the interaction of Congo red with DNA is intercalation binding. The binding stoichoimetry of nCR:nDNA=1:1, and the binding constant is KӨ25℃=4.50×103 L/mol. The thermodynamic parameters at 25℃are ΔrHmӨ =7.04×104 J/mol, ΔrSmӨ=305.88 J/(mol•K), ΔrGmӨ =－2.08×104 J/mol respectively. Entropy is driven force.
