The IGF-1 proteins isolated from the IgG-sepharose column were separated on a 2-D focusing/phoresis acrylamide gel. Five μg of the IGF-1 – S. aureus fusion protein was loaded on a 10% bis-acrylamide gel for electrofocusing and phoresis. Electrofocusing was conducted initially over a pH range of 4–10. Following isoelectric focusing and electrophoresis, four proteins (6, 7, 14 and 25 kDa) were detected after Coomassie Blue staining. These proteins corresponded in molecular weight to ZZ-IGF-1 (A), Z-IGF-1 (B) and IGF-1 (C).