Purification of foetal steroid-binding protein from human serum by affinity chromatography on 5 alpha-androstane-3 beta,17 beta-diol 3-hemisuccinate-aminohexyl-Sepharose 6B.

In order to develop an immunoassay for foetal steroid-binding protein in human serum, which is impossible to assay quantitatively in normal samples by conventional ligand-binding techniques, the protein was purified by salt precipitation, affinity chromatography and gel filtration. Elution was by competing ligand or alkaline pH. The purified protein was further characterized and a highly specific antiserum was raised in rabbits.