Chinese Journal of Physiology

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Chinese Journal of Physiology, 1929, Voi. III, No, 1, pp, 1—6,

STUDIES ON DENATURATION OF PROTEINS VII. DENATURATION VERSUS COAGULATION

HSIEN WU (From the Department of Biochemistry, Peking Union Medical College, Peping) Received for publication August 24, 1928

Hardy (4) in 1899 put forth the view that heat coagulation of proteins takes place in two stages, the first of which, denaturation, is a preliminary change in the chemical structure of the protein, while the second, flocculation, is a purely physical process. This view was adopted and amplified by Chick and Martin (2) who defined denaturation as the reaction between the protein and hot water and used the term agglutination to designate the process of the separation of the denatured protein in a particulate form. That the protein can be separately denatured and flocculated has been confirmed by others, and the composite nature of coagulation seems to be generally accepted.

According to this view heat coagulation is nothing more than denaturation followed by flocculation (or agglutination). Since flocculation is physical, it has been customary in previous investigations, including those of ourselves, to regard denaturation and coagulation as one and the same process as far as any chemical change is concerned. Consequently, conclusions regarding denaturation have been drawn from experiments primarily on coagulation, and vice versa, This has led to two theories of heat coagulation (or denaturation) of protein which are diametrically opposite to each other. According to one theory, denaturation (and therefore coagulation) is a mild hydrolysis or degradation; (5, 11, 12) according to the other, coagulation (and therefore denaturation) is a dehydration or condensation (7, 8). The chemical identity of the coagulated protein with the denatured and flocculated protein does not seem to have been questioned.