1. The Institute of Physical and Chemical Research (RIKEN), Hirosawa 2‐1, Wako, Saitama 351‐01, Japan.,
2. Faculty of Textile Science and Technology, Shinshu University, Tokida 3‐15‐1, Ueda, Nagano 386, Japan.,
3. Department of Biotechnology, University of Tokyo, Yayoi 1‐1‐1, Bunkyo‐ku, Tokyo 113, Japan.