[Binding of small molecules with nucleic acids having tertiary structure]

A model has been developed which allows description of the binding of antibiotics and dyes to a nucleic acid in which different regions are involved in the formation of a certain tertiary structure. Interactions between different segments of nucleic acid may contribute to the internal overall energy of the macromolecule. We consider the case when the tertiary structure and the internal energy of the macromolecule are altered upon binding of small molecules. These structural changes affect the shape of the binding isotherm of ligand to the nucleic acid. We obtain relations which permit to determine the dependence of the internal energy on the degree of binding of ligand to nucleic acid.