부산대학교 도서관

RADIOIODINATED polypeptide hormones are widely used as tracers for both radioimmunoassay and in vivo metabolic studies. The process of iodination may induce gross chemical changes which are detectable by physico-chemical techniques, but such techniques may not reveal more subtle changes reflected only in decreased biological activity. Such a situation arises with gastrin, in which iodination of the synthetic hormone by the chloramine-T method1results in almost total loss of biological activity. This is due to oxidation of the methionyl residue at position 15, which is in the biologically active C-terminal tetrapeptide sequence, and can be prevented by modifying the iodination procedure. The resulting iodinated gastrin has full biological activity, is labelled to the same specific activity as in the original method, and has an increased affinity for antibodies to the hormone.