1. Laboratory of Single-Molecule Cell Biology, Kyoto University Graduate School of Biostudies, Kyoto 606-8501, Japan
2. Department of Pharmacology, Kyoto University Graduate School of Medicine, Kyoto 606-8501, Japan
3. Laboratory of Single-Molecule Cell Biology, Tohoku University Graduate School of Life Sciences, Sendai, Miyagi 980-8578, Japan
4. Department of Physics, Lehigh University, Bethlehem, PA 18015