Abstract: PREPARATION OF HIGHLY PURIFIED 125IVENOMNEURAL GROWTH FACTORLiu Xiuwen\ Tang Zhongming\ Chai Biaoxin(Institute of Radiation Medicine,Academy of Military Medical Science, Beijing 100850)Wang Jiazheng(Institute of Basic Medicine, Academy of Military Medical Science, Beijing 100850)ABSTRACTThe highly purified and bioactive 125IvNGF is prepared. The high performance ionexchange chromatographic(HPIEC) profile of nonlabeled vNGF is appeared as a single peak eluted at about 0.4 mol/L-1NaCl. After 125I labeling and purification with Saphacryl HR200, the HPIEC profile of labeled protein exhibits a new large molecule that is not absorbed on the cation column. The result suggests that there may be aggregation and surface electronic changes during the labeling. After the second separation using SepharoseSP to remove the nonabsorbed component, a 97% 125IvNGF is obtained. The bioassay of 125IvNGF demonstrates the good biological activity. The result suggests that it is important to design an optimal purification method, according to the physical chemistry property of the labeled protein.Key words cobra venom neural growth factor 125I　labeling purification bioassay