Institution: | a Department of Physics, Sevastopol National Technical University, Studgorodok, Sevastopol 99011, Ukraine b The Randall Centre for Molecular Mechanisms of Cell Function, King's College, Guy's Campus, London Bridge, London SE1 1UL, UK c Department of Physics and Mathematics, Autonomous University of Puebla, Mexico 72570, Mexico d School of Biological and Chemical Sciences, Birkbeck College, University of London, Malet Street, London WC1E 7HX, UK |
Abstract: | The self-association of a bis-intercalator, ethidium homodimer (EBH), and its hetero-association with phenanthridine dye, propidium iodide (PI), have been studied by 1D and 2D 1H NMR spectroscopy using the analysis of proton chemical shifts changes in aqueous solution as a function of concentration and temperature. Experimental results have shown that dynamic equilibrium in solution includes different conformational states of EBH molecules: folded (F) and unfolded (U) forms, a dimer form (F2) where an aromatic chromophore of one of EBH molecules is inserted (intercalated) between the linked chromophores of the other homodimer molecule and a trimer complex (F3) with two partitially intercalated aromatic chromophores between the chromophores of the folded EBH molecule. It has been found that EBH associates with propidium iodide forming 1:1 complex, where PI is inserted between the chromophores of the folded form, and 1:2 complex resulting from intercalation of PI into F2 EBH dimer. Thermodynamical parameters of EBH self-association and complexation between EBH and PI have been determined and conclusions about the nature of the physical forces responsible for the formation of intermolecular complexes have been made. |