1. Biology Department, De La Salle University, 2401 Taft Avenue, 0922 Manila, Philippines
2. Department of Chemistry, Kurume University School of Medicine, 830-001 Kurume, Japan
3. Laboratory of Biological Chemistry, Department of Chemistry, Faculty of Science, Hokkaido University, N10 W8, Kita-ku, 060-0810 Sapporo, Japan