1. School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho, 4259-B55, Midori-ku, Yokohama 226-8501, Japan
2. SR Life Science Instrumentation Unit, RIKEN/SPring-8 Center, 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan