1. Faculty of Science, Kwansei Gakuin University, Uegahara, Nishinomiya 662, Japan, M&S Technosystems, 2-12-4 Mikuni-Honmachi, Yodogawa-ku, Osaka 532, Japan, and Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK