The influence of the ionic strength of the medium and the nature of counterions on the interaction of DNA molecule with derivatives of actinocin and isoquinoline

Abstract

In this work the interaction of the DNA molecule with derivatives of actinocin and isoquinoline was studied by spectral, calorimetric and hydrodynamic methods under different ionic strength of the medium. All investigated compounds formed reversible equilibrium complexes with the DNA molecule. When μ = 0.1, the flat heterocyclic chromophores of the compounds either intercalated in the DNA double helix or located in one of the grooves, depending on the length of the alkyl chain linking the chromophore with protonated groups of actinocin derivatives. With the decrease of ionic strength there was an increase in affinity of all investigated compounds to DNA and second mode of interaction, leading to the formation of intercalated dimers, added to the intercalation binding. Not intercalating ligands (in a high ionic strength) changed the mode of binding and behaved like intercalators, causing an increase in contour length of the macromolecule, while the ionic strength decreased to 0.001. Refs 21. Figs 5. Tables 3.