Fibroblast Growth Factor-acidic Bovine (FGF-1) purified from Bovine Brain contains a 17 kDa and a 20 kDa polypeptide chain. The 17 kDa peptide is derived from the 20K peptide by restricted proteolysis. (See Jaye et al²). The FGF acidic is purified by proprietary chromatographic techniques.