Differences in the binding of methylated albumin to non-replicating, replicating and denatured DNA from Ehrlich ascites cells.

The binding of methylated albumin to DNA, the basis of the chromatography on columns of kieselguhr coated with methylated albumin (MAK chromatography), was investigated. Scatchard plots revealed only one mode of interaction with fully double-stranded DNA. The complexes should be completely dissociated by raising the NaCl concentration of the solution to 0.8 M, indicating a binding by electrostatic attraction between the oppositely charged protein and DNA molecules. In complexes with denatured and partially single-stranded replicating DNA an additional kind of binding was found which made these complexes more stable against salt dissociation. These secondary interactions were stronger at 23 degrees C than at 0 degrees C and could be weakened by the addition of 6 M urea. It was therefore concluded that apolar forces were involved in these interactions.