A method for the purification of bovine somatomedin C

The large scale purification of bovine somatomedin C has been achieved using a protocol that includes cross-flow ultrafiltration of fresh bovine plasma, treatment of the concentrated plasma with formic acid and ethanol, removal of the insoluble material by high speed centrifugation, cross-flow ultrafiltration of the formic acid and ethanol-soluble proteins, ion exchange chromatography, gel filtration and preparative isoelectric focusing. Thirty L of bovine plasma containing 2.16 kg protein were processed to yield approximately 170 micrograms of highly purified bovine somatomedin C. This represents an 840,000-fold purification of this peptide. The purified peptide has a molecular weight of 10,200 daltons, an isoelectric point of 8.5 and a specific activity of 11,750 Units/mg protein.