Isolation of thyroxine-binding globulin (TBG) by immunoadsorption chromatography: some physical and immunochemical characteristics of TBG.

Thyroxine-binding globulin (TBG) was isolated from pooled whole human serum by diethylaminoethyl (DEAE) Sephadex anion exchange chromatography followed by immunoadsorption chromatography on a cyanogen bromide-activated Sepharose 4B-sheep anti-human TBG immunoadsorbent. Sodium dodecyl sulphate (SDS)-poly-acrylamide gel electrophoresis (PAGE) of the purified TBG revealed a major protein band with a molecular mass of 65 000 and a weak band of molecular mass 54 000 in both reducing and non-reducing buffers. Sedimentation velocity analysis revealed an S20,w coefficient of 4.5S and a calculated molecular mass of 60 000. Immunochemical analysis confirmed the purity of the TBG preparation which gave a single precipitin peak on two-dimensional immunoelectrophoresis.