Nature of Heat Denaturation of Proteins

Chick and Martin (1) have shown that the heat coagulation of proteins consists of two distinct processes; tiiz., (a) denaturation, the alteration of the protein under the influence of heat, and (b) agglutination, the separation of the altered protein in a particulate form. Agglutination, in which hydrogen ion concentration and electrolyte contents play important roles (2), is now a fairly well understood phenomenon of colloidal chemistry, while the significance of denaturation is st,ill obscure. Although denaturation is made evident by agglutination, the latter is not a necessary consequence of the former. In this paper we are concerned only with the alteration which heatrcoagulable proteins undergo under the influence of heat, and we will designate it as heat denaturation to distinguish it on the one hand from denaturation by other agencies and on the other from heat coagulation, which would include the physical process of agglutination. No little confusion in the literature has resulted from the failure to distinguish the two processes comprised in heat coagulation of proteins. The word denaturation is used loosely to designate the change of proteins from a soluble to an insoluble form brought about by a large variety of chemical and physical agents, including acids, alkalies, alcohol, acetone, salts of heavy metals, alkaloidal reagents and dyes (3), and heat, light, and pressure (4). Chick and Martin (5) consider heat denaturation as a reaction between protein and water which implies in all probability a hydrolysis. Robertson,’