1. a Department of Polymer Engineering, Chonnam National University, Kwangju 500-757, Korea
2. b Kanagawa Academy of Science and Technology, Takatsu-ku, Kawasaki 213, Japan
3. c Kanagawa Academy of Science and Technology, Takatsu-ku, Kawasaki 213, Japan
4. d Faculty of Agriculture, Nagoya University, Chikusa-ku, Nagoya 464-01, Japan
5. e Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 227, Japan