Technological method of isolation of human alpha-fetoprotein. Estimation of free sulfhydryl and amino groups status in the purified preparation

Abstract

A new preparative method for the isolation of human alpha-fetoprotein (AFP) from cord blood serum was described. This involves the precipitation of high-molecular compounds with polyethylene glycol and the affinity, ion exchange, and gel permeation chromatographies. Up to several tens of milligrams of the homogeneous AFP can be rapidly (48 h) prepared per isolation cycle in a high yield. The native structure of the isolated AFP was proved by immunochemical analysis. No free sulfhydryl groups were found in the purified AFP, and its reduction with dithiothreitol at 4 degrees C led to the formation of two sulfhydryl groups probably belonging to the Cys18 and Cys67 residues in domain I of the protein molecule. Up to ten amino groups in the purified AFP were shown to be accessible for a mild modification by 3-(2-pyridyldithio)propionic acid N-succinimide ester.