No abstract

The formation of soluble complexes through the interactions of macromolecules bearing net charges of the same sign is a phenomenon of considerable interest. Particular examples of this type of complex may be found in the antigen-antibody system (e.g. Singer & Campbell, 1955a, b, c; Singer, Eggman & Campbell, 1955), the polymerization of acid insulin (Oncley, Ellenbogen, Gitlin & Gurd, 1952; Doty & Myers, 1953), the polymerization of oc-chymotrypsin (Kegeles & Rao, 1958), the interaction between nucleic acids and proteins (Goldwasser & Putnam, 1950) and the interactions of plasma proteins with charged polysaccharides (Walton, 1952; Noguchi, 1956; Bernfeld, Donahue & Berkowitz, 1957; Sasaki & Noguchi, 1959). The work reported in this paper is an investigation, with free-boundary electrophoresis, of the effect of variations of pH, ionic strength and molecular size on the formation of soluble complexes between bovine plasma albumin and synthetic derivatives of dextran. Two types of dextran derivatives have been employed: a sulphate ester and an ether-linked diethylaminoethyl derivative. Interactions between the bovine plasma albumin