1. Quantum Beam Science Directorate, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Tokai, Ibaraki 319-1195, Japan, Department of Biological Science, Graduate School of Science, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan, and Lead Discovery Research Laboratories, Astellas Pharma, Inc., 21 Miyukigaoka, Tsukuba, Ibaraki, 305-8585, Japan