DUPLEX–TRIPLEX TRANSITION IN COMPLEXES OF NUCLEIC ACIDS WITH HOECHST 33258

Abstract

The study of complexes of groove binding ligand Hoechst 33258 (H33258) with Calf Thymus DNA has been carried out. The data obtained revealed that the melting curves of the complexes of H33258 with DNA are monophasic at low ligand concentrations (0 < r ≤ 0.2) and become biphasic at relatively high concentrations (0.2 < r ≤ 0.33). This effect was revealed to depend on the ionic strength of the solution, and can also occur at high concentrations of the ligand. Comparison of the obtained data with the results for poly(rA)-poly(rU) and poly(dA)-poly(dT) shows a coincidence in the case of DNA and poly(rA)-poly(rU), while in the case of poly(dA)-poly(dT) the melting curves become biphasic at low ligand concentrations and actually do not depend on the ionic strength of the solution.