Thermal denaturation of complexes of DNA with sequential and random lysine containing polypeptides

Abstract

Complexes of DNA with lysine containing sequential polypeptides and random amino-acid copolymers were studied using the method of thermal melting. The effect of lysine content, lysine distribution along the polypeptide chain and of the lysine/nucleotide input ratio on the melting pattern was determined. Polypeptide redistribution on DNA and reversibility of the DNA melting in individual transition were also tested. It was shown that the behavior of DNA complexes of polypeptides with relatively low density of lysine differed from that of lysine rich polypeptides due to a low degree of charge neutralization and to the possibility of polypeptide redistribution during melting in the former case. In the later case the binding was found to be essentially irreversible. Higher thermal stability and lower redistribution rate were obtained using complexes prepared by gradient dialysis as compared with those prepared by direct mixing.