1. Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 001-0021, Japan, Hitachi High-Technologies Co., Hitachinaka 312-8504, Japan, Naka Customer Center, Hitachi Science Systems Co., Hitachinaka 312-8504, Japan, and Hitachi Research Laboratory, Hitachi Ltd., Hitachi 319-1292, Japan