1. Pharmaceutical School; Xinxiang Medical Univ.; Xinxiang 453003 Henan China
2. Chemical and Pharmaceutical School; Henan Univ. of Science and Technology; Luoyang 471003 Henan China
3. Dept. of Microbiology, Inst. of Basic Medical Sciences, Chinese Academy of Medical Sciences & School of Basic Medicine; Peking Union Medical College; Beijing 100005 China