The Molecular Size of Proteins from Several Wools Solubilized in Aqueous Urea

Abstract

The soluble proteins isolated from normal wools differing widely in geographical origin, fineness, and breed show the same behavior in ultracentrifugation and diffusion. The wool protein, made soluble in aqueous 10M urea by reduction, has a sedimentation constant ap proaching 1.2 S at zero protein concentration, referred to water at 20°C. In the presence of 0.2N lithium chloride the limiting sedimentation constant is 1.6S. The sedimentation con .stant increases with decreasing concentration of either protein or urea. Similar values are found in other media. The diffusion constant of 2% to 3% solutions is 4.9 × 10-7 cm.2 sec.^-1, referred to water at 20°C. Corresponding sedimentation and diffusion measurements give the average molecular weight, 14,000, and the unusually high molar frictional ratio, 2.8, suggesting high asymmetry, high solvation, or a combination of these.