Abstract: STUDY OF A DIRECT METHOD FOR ~(99)Tc~m LABELING OF MONOCLONAL ANTIBODY Ⅱ.THE EFFECT OF ASCORBIC ACID IN THE DIRECT LABELINGSang Lixing; Wu Yonghui; Liu Bin; Liu Yuangfang(Department of Technical Physics, Peking University, beijing 100871)Zhang Meiying; Lin Baohe; Yang Zhi;Fang Yongxin(Department of Nuclear medicine, Beijing(Tumor MoAb Department of PLA General Cancer Institute, Beijing 100034)Hospital, Beijing 100853)Abstract:The effectes of ascorbic acid(AA) on the process of direct labeling of monoclonal antibody are investigated. Based on the comparison of the relevant experimental conditions, it is found that AA has a strong antixidizing effect on reduced antibody and also a stabilizing effect on the labels.Monoclonal antibody fragments F(ab') 2 are successfully labeled using our method. Biodistribu tions of the labels are measured in tumor bearing nude mice. Tumor localization in vitro is also achieved.Keywords:~(99)Tc~ m Drect labeling Monoclonal antibody Ascorbic acid Free sulfhydryl group