Fractionation of immunoreactive cholecystokinin by adsorption to QUSO or talc

The technique of adsorption of peptides containing basic amino acids to surfaces of silica or talc has been extended to distinguish between the basic precursor peptides, cholecystokinin (CCK33) and its variant (CCK39), and their COOH-terminal 12 and 8 amino acid fragments (CCK12 and CCK8) in plasma and tissue extracts. CCK39 and CCK33 are quantitatively adsorbed from 2 ml of solution by 5 mg QUSO G32 or 25 mg talc. The adsorbed basic peptides can be completely eluted from QUSO but not from talc by 0.1N HC1. CCK12 and CCK8 are not detectably adsorbed by either QUSO or talc. The method is simple, inexpensive and is suitable for rapid handling of multiple samples