Serum Protein Fractionation by Membrane Processes: Centrifugal Ultrafiltration, Osmosedimentation, and Multistage Ultrafiltration

Abstract

Whole sera proteins may be fractionated according to their molecular weights by using three membrane techniques: centrifugal ultrafiltration, osmosedimentation, and multistage ultrafiltration. Ultrafiltration or dialysis cells were mounted in the swinging baskets of a centrifuge in all three cases, with the membranes aligned parallel to the centrifugation radius. As a result, solute accumulated over the membrane was convectively removed from its surface, thus preventing membrane polarization and fouling. During these experiments, smaller proteins migrated across the membrane, leaving behind the larger ones. Multistage filtration experiments were performed using cells fitted with three different membranes of successively narrower pores. Four different fractions were thus obtained and analyzed by gel permeation chromatography; separation factors as high as 2000 were obtained.