1. Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1, Oe-honmachi, Kumamoto 862-0973, Japan, Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1, Kurokami, Kumamoto 860-8555, Japan, Department of Physical Chemistry, Graduate School of Pharmaceutical Sciences, Chiba University, Inage-Yayoi, Chiba 263-8522, Japan, and Department of Physical Chemistry, Kyoto Pharmaceutical University, Yamashina, Kyoto 607-8414, Japan