The synthesis of sub-micron magnetic particles and their use for preparative purification of proteins

A novel one‐step protocol for the preparation of sub‐micron magnetic particles as small as 30 nm in diameter has been developed. The surface of the particles was functionalized with carboxyl groups (∼1 COOH per 15Å2) to facilitate the attachment of affinity ligands. The high surface area of the resulting beads, combined with the high density of functional groups on the surface, makes them ideally suited for the preparative purification of proteins as was demonstrated by the efficient isolation of trypsin (36 mg per gram of particles) from pancreatic extract. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 419–424, 1998.