1. Department of Bacteriology, Faculty of Medicine, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, 113-8421
2. Japan Atomic Energy Research Institute, Tokai, Ibaraki, 319-1195
3. Advanced Science Research Center
4. Department of Physics, Faculty of Medicine, Juntendo University, Inba-gun, Chiba, 270-1695, Japan