Water-soluble lysine-containing polypeptides. VI. A study of annealed complexes between calf thymus DNA and the following copolymers: poly-(L-lysyl-X), where X = Gly, L-Ala, L-Val, L-Leu, and L-Phe

Turbidity measurements, circular dichroism spectra, electron micrographs, and thermal-optical measurements have been made on complexes between sonicated DNA and several polypeptides with the following structure: poly-( L -lysine- L -X) where X = Gly, Ala, Val, Leu, Phe. The results are influenced by any method of polypeptide synthesis which results in chain branching of the polypeptide. When polypeptides prepared by the same synthetic route are incorporated into the complexes the results also depend on the polypeptide used. Five possible explanations are offered as sources of the latter observations.