1. Department of Material Development, Takasaki Radiation Chemistry Research Establishment, Japan Atomic Energy Research Institute, 1233 Watanuki, Takasaki, Gunma 370-12, Japan, Department of Bioscience, Teikyo University of Science, Uenohara, Kitatsuru, Yamanashi 409-01, Japan, and Department of Chemistry, Gunma University, Tenjin-cho, Kiryu, Gunma 376, Japan