Affinity chromatography with amniotic fluid somatomedin binding protein in the purification of insulin-like growth factor I.

A simplified procedure has been developed for the isolation of insulin-like growth factor I from human plasma by use of affinity chromatography with the somatomedin binding protein. After acidification of human plasma and separation of insulin-like growth factor I and endogenous binding protein by cation exchange chromatography on SP-Sephadex the material was passed through a column packed with pure human amniotic fluid binding protein covalently coupled to Sepharose. The bound insulin-like growth factors I and II were eluted by 1M acetic acid and separated on a Mono S cation exchange column by use of a salt gradient. The 30 micrograms insulin-like growth factor I and 18 micrograms insulin-like growth factor II recovered from 1 liter plasma gave an overall recovery of 30% for insulin-like growth factor I but only 2.5% for insulin-like growth factor II.