Determination of the Isosbestic Point in the Absorption Spectra of DNA-Ethidium Bromide Complexes

We propose a procedure for mathematical treatment of the spectra of complexes between ligands and DNA, which allows us to determine the position of the isosbestic point with high precision. As a specific example, we consider the absorption spectra of ethidium bromide complexes titrated against a DNA solution. As a result of using the method, besides the main type of binding we have identified the appearance of additional types of binding between the ethidium bromide and DNA.