Abstract: A COMPARATIVE STUDY ON THE IODINE-LABELED METHODS OF PROTEIN AND POLYPEPTIDE Li Huaifen Niu Huisheng Yuan Mingyue Yu Jinghui（Institute；of Rodiation．Medicine,Chinese Academy of，Medical Sciences, Tianjin300192）ABSTRACT There are three methods：chloramine-T，Iodogen and lactoperoxidase（LPO）．~(125)I-ACTH，~(125)I-in-sulin and~(125)I-HSA are prepared by these techniques．The resuIts show that lactoperoxidase is isolatedand purified from fresh milk，meanwhile，the enzyme is used a experiment of~(125)I－labeled protein，Pep-tide hormone and monoclone antibody，etc．LPO is a very successful meththod for it＇s mild，completereaction, controliable，highet labelling yield，higher purity of iodine- labeled compound and so on.Itremains biological activation and stdble character more than other two techniques. Key words ~(125)I-labeled compound chloramine-T Iodogen lactoperoxidase