Spectral study of the binding of doxorubicin to calf thymus DNA

The self-association of doxorubicin in aqueous solutions was considered in terms of a dimerization equilibrium, and the dimerization constant (K-d), the molar absorption coefficient of the monomer (epsilon(M)) and dimer (epsilon(D)) were determined, The binding constant of doxorubicin to DNA at small and medium values of the polymer to drug concentration ratio (P/D) was determined using Schwarz and Wolfe methods under two different conditions: at constant drug concentration and variable polymer concentration, and at constant polymer to drug ratio, The dependence of the binding constant on the Na+ ions concentration was studied. From this dependence, the electrostatic and nonelectrostatic contributions to the binding free energy of doxorubicin to DNA were evaluated.