SEPARATION OF GROWTH-STIMULATING ACTIVITY OF BSA FRACTION-V FROM THE BULK OF ALBUMIN USING HEPARIN SEPHAROSE CHROMATOGRAPHY

Bovine serum albumin (BSA) is a potential source of biological contami nation in cell culture medium. The aim of this work was to attempt to replace BSA in low serum and serum-free medium (SFM). BSA fraction V w as subjected to a variety of processes in order to determine if the gr owth promoting activity observed for NRK cells could be extracted from the BSA molecule. These included solvent extractions, diafiltration, reverse phase HPLC and affinity chromatography using heparin sepharose . Solvent extraction and diafiltration failed to remove the activity f rom the BSA. Affinity chromatography using heparin sepharose indicated that all of the activity observed with BSA was retained in the 0.5 M NaCl fraction and was associated with less than 3% of the original pro tein. The major protein band in the 0.5 M NaCl fraction had the same a pparent molecular weight as albumin (as seen by SDS-PAGE and analytica l reverse phase HPLC). Unlike the untreated BSA, the 0.5 M NaCl fracti on was partially susceptible to proteolytic digestion and to variation s in pH.