Purification of placental alpha-1-foetoprotein

Quantitation of placental alpha-1-foetoprotein was done by the radioimmunoassay technique and gave a mean value of 6060 +/- 22.2 ng/g fresh tissue. The purification process included three methods. (1) Protein precipitation was performed using ammonium sulphate at 50 and 70% saturation. Elution on a Concanavalin A-sepharose column was used to diminish the interference of albumin with alpha-foetoprotein. (2) A coupling immunoadsorption technique using CNBr-activated Sepharose 4-B, antialbumin and antitransferrin, was found to be more reproducible. (3) Counter-immunoelectrophoresis and discontinuous gel electrophoresis gave a 60% yield with a 400-fold purification.