Fluctuations in order–disorder transitions in the DNA–ligand complexes with various binding mechanisms

The melting of the DNA–ligand complex is considered theoretically for the ligands binding with the DNA by two mechanisms. The obtained results describe the experimentally observed behavior of such quantities as the denaturation degree and the correlation length depending on the concentration of ligands. It is shown that the heat and cold denaturations of the DNA–ligand complexes exhibit the same cooperativity, as the heat denaturation of the pure DNA. At the same time, the temperature range of the cold denaturation is essentially narrower than the interval for the heat denaturation of the pure DNA and the DNA–ligand complexes.