DNA-protein interaction studied in model systems

Conditions for the formation of interpolymer complexes of DNA with insulin, cortexin, and cytochrome C in the neutral pH range were studied by UV spec troscopy, gel-permeation chromatography, and membrane diffusion techniques. The selected proteins differ in their acid-base properties and do not belo ng to natural DNA ligands. The DNA-protein complexes remained stable when t he ionic strength of solution was increased up to 0.5 mol/l. The isotherms of DNA binding to proteins in solutions with an ionic strength of 0.3 mol/l and pH 7.8-8.2 exhibit a cooperative character. The intrinsic viscosity of DNA in the presence of proteins studied decreases proportionally to the am ount of bound protein.