Low binding of Bolton-Hunter-labelled cholecystokinin-33 to carboxyl-terminal CCK-antibodies.

Labelling of cholecystokinin-33 (CCK33) with [125I]hydroxyphenylpropionic acid-succinimide ester (Bolton-Hunter-reagent) results in labels with excellent immunoreactivity when tested with non-carboxyl-terminal CCK-antibodies but extremely low binding to carboxyl-terminal CCK-antibodies. This finding might explain some of the difficulties experienced with production of immunoreactive CCK33 labels prepared by the Bolton-Hunter method.