1. Department of Bioinformatics, College of Life Sciences, Ritsumeikan University, 1-1-1, Noji-higashi, Kusatsu, Shiga 525-8577, Japan
2. Department of Computer Science, School of Computing, Tokyo Institute of Technology, W8-76, 2-12-1, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
3. Toyota Physical and Chemical Research Institute, 41-1, Yokomichi, Nagakute, Aichi 480-1192, Japan