1. Department of Chemistry Faculty of Science Hokkaido University North-10 West-8, Kita-ku Sapporo Hokkaido 060-0810 Japan
2. Current address: Institute for Integrated Cell-Materials Sciences Kyoto University Kyoto 606-8501 Japan
3. Faculty of Information Science and Technology Hokkaido University North-14 West-9, Kita-ku Sapporo Hokkaido 060-0814 Japan