Voltammetric studies of the interaction of methylene blue with DNA by means of β-cyclodextrin

The formation of an inclusion complex of methylene blue with beta-cyclodextrin is testified by voltammetry and spectroscopy and its stable constant is determined to be 4.4 x 10(3) M-1. The interactions of methylene blue and the inclusion complex with DNA have been investigated by means of voltammetry. The binding constants of methylene blue and the inclusion complex to DNA are obtained through the changes of peak currents and their values are 1.1 x 10(4) M-1 and 7.2 x 10(3) M-1, respectively. The experimental results reveal that the inclusion complex does not decompose when it interacts with DNA, and beta-cyclodextrin itself does not interact with DNA. Their binding numbers (n) are 1 both methylene blue and the inclusion complex. According to the experimental data, it can be inferred that the binding model of methylene blue to DNA may be 'electrostatic binding' under our experimental conditions. This can clearly explain the experimental phenomena. (C) 1999 Elsevier Science B.V. All rights reserved.