1. Department of Bioinformatic Engineering, Graduate School of Information Science and Technology, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan, Exploratory Research for Advanced Technology (ERATO), Japan Science and Technology Agency, Tokyo 135-0064, Japan, and Department of Frontier Biosciences, Graduate School of Frontier Biosciences, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan