Dependence of optical rotatory dispersion of globular proteins on ionization and denaturation

The following proteins were studied by means of spectropolarimetry: human serum albumin, bovine serum mercaptalbumin, β-globulin (metal-binding), γ-globulin, Bence-Jones protein, ovalbumin, chymotrypsinogen, pepsin, rennin, trypsin inhibitor, taka-amylase, and bacterial amylase. It was ascertained that the one-term linear Drude equation holds in all instances of native and denatured proteins. The dependence of the dispersion constant ( λ 0) on pH of the solutions was studied on most of these proteins. Denaturation by acid, alkali, heat, guanidine thiocyanate, and the detergent sodium dioctyl sulfosuccinate also was investigated with some of the proteins. Pepsin, rennin, γglobulin, and Bence-Jones protein exhibited an increase in their dispersion constants on denaturation.