Binding Parameters of Mitoxantrone and Ethidium Bromide with A-Form Nucleic Acids Based on Adsorption Isotherms

An analysis of adsorption isotherms was carried out based on experimentally obtained data on the binding of the antitumor compound mitoxantrone (MTX) and ethidium bromide (EB) to A-form nucleic acids (NA). The obtained results show that there is selectivity in binding with base pairs of NA. Calculations show that the enthalpy changes due to the binding of MTX and EB to A-form NA (within the experimental error) are almost the same, but the entropy changes upon binding are significantly different. Generalizing the obtained experimental data and comparing them with the literature, it can be concluded that the binding of these compounds to the B-form is stronger compared to the A-form, leading to a more pronounced change in the structure of the double helix of NA.