An improved procedure for isolation of thyroxine-binding globulin from human pregnancy serum

A convenient method for isolation of TBG from human pregnancy serum is reported. The method is based on batch-wise treatment of serum with hydroxyapatite followed by batch-wise adsorption of TBG to an affinity gel consisting of Sepharose to which thyroxine was bound with a spacer group. After selective desorption the TBG-preparation was practically pure. The small amounts of contaminating proteins were easily removed by affinity chromatography on Concanavalin A-Sepharose. The resulting preparation was shown to be homogeneous by polyacrylamide gel electrophoresis and immunological techniques.