PURIFICATION OF INSULIN-LIKE GROWTH-FACTOR-I AND RELATED PROTEINS USING UNDERIVATIZED SILICA

Adsorption chromatography using underivatized porous glass can be an e ffective capture step for the purification of recombinant proteins. Cl assical desorption techniques using chaotropic agents or harsh chemica l solvents often result in elution of inactive material and may not be economical at the process scale. More recently, elution schemes have used tetramethylammonium chloride (TMAC) to obtain biologically active material. A TMAC elution was shown to be effective in the initial pur ification steps for the recovery of recombinant human insulin-like gro wth factor-I (rhIGF-I) from an Escherichia coli fermentation broth. Ho wever, TMAC also elutes other, more hydrophobic, proteins that are dif ficult to remove in subsequent purification steps. This paper describe s the capture of IGF-I from a crude fermentation broth and a more spec ific elution using a combination of ethanol and NaCl rather than TMAC. This elution also can be used with other proteins including an IGF-I binding protein (BP3) expressed in mammalian cell culture.