Sex Steroid Binding Plasma Protein (Sbp)

The detection, preparation from plasma Cohn fraction IV and purification of SBP are reported. The association constant has the value of K = 1.2 and 0.5 10 9 M− 1 at 4°C for testosterone and oestradiol, respectively. A preparation homogeneous by the criteria of polyacrylamide gel electrophoresis, binding studies and ultracentrifugation is obtained; sedimentation equilibrium experiments give a molecular weight of approx. 52 000, confirming the approximative value obtained from Sephadex filtration.