Optical rotation and viscosity of native and denatured proteins. II. Influence of temperature and concentration

Abstract

The rotation values of native serum albumin, γ-globulin, and lysozyme increase with increasing temperature, but those of pepsin decrease. There is a maximum of specific rotation at medium concentrations of native serum albumin, ovalbumin, lysozyme, γ-globulin, chymotrypsinogen, and β-lactoglobulin. In the denaturation of γ-globulin with 1.5 M guanidine hydrochloride, of chymotrypsinogen with 2 M guanidine hydrochloride, or of lysozyme with 4 M guanidine hydrochloride at 25 °C., both optical rotation and viscosity increase in time until constant values are reached. A further increase in levorotation and viscosity takes place upon heating at 50 or 55 °C. with the mentioned reagent. Denaturation of serum albumin with potassium thiocyanate or guanidine hydrochloride, of γ-globulin with guanidine hydrochloride or potassium thiocyanate, and of pepsin, chymotrypsinogen, and lysozyme with guanidine hydrochloride are irreversible processes. The original properties of the proteins are only partly restored or much changed if the protein is liberated from the denaturing agent.