Thermodynamic analysis of complex formation of ethidium bromide with DNA in water solutions

A thermodynamic analysis of two types of binding of ethidium bromide with DNA: intercalation and binding to the outer surface of a biopolymer has been performed by spectrophotometry. It has been shown that the dominant contribution to the energy of external binding of the ligand to DNA is made by hydrophobic interactions, which lead to less negative values of enthalpy and entropy and more severe negative changes in the heat capacity of complex formation as compared with the intercalation type of binding.