A radioimmunoassay for the determination of insulins from several animal species, insulin derivatives and insulin precursors in both their native and denatured state.

Antibodies were raised against the carboxy terminus of the insulin A chain in sheep, goat and rabbit using as antigen the synthetic octapeptide YQLENYCN conjugated to bovine serum albumin (BSA). All of the antisera obtained cross-reacted with molecules containing this peptide sequence. Using these antibodies, we developed a radioimmunoassay that could detect the insulin A chain itself, both denatured and natural mammalian and avian insulins, as well as proinsulins and insulin fusion proteins from microorganisms.