On the Structure of Native, Denatured, and Coagulated Proteins

In this paper a structural theory of protein denaturation and coagulation is presented. Since denaturation is a fundamental property of a large group of proteins, a theory of denaturation is essentially a general theory of the structure of native and denatured proteins. In its present form our theory is definite and detailed in some respects and vague in others; refinement in regard to the latter could be achieved on the basis of the results of experi- ments which the theory suggests. The theory (some features of which have been proposed by other investigators) provides a simple structural interpretation not only of the phenomena connected with denaturation and coagulation which are usually discussed (specificity, solubility, etc.) but also of others, such as the availability of groups, the entropy of denatura- tion, the effect of ultra-violet light, the heat of activation and its depen- dence on pH, coagulation through dehydration, etc. I. The experimental basis upon which the present theory rests will be briefly described. 1. The most significant change that occurs in denaturation is the loss of certain highly specific properties by the native protein. Specific differences between members of a series of related native proteins and specific enzy- matic activities of native proteins disappear on denaturation, as the fol- lowing observations demonstrate : (a) Many native proteins can be crystallized and the crystal form is characteristic of each protein. No denatured protein has been crys- tallized.