1. Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA;
2. Laboratory for Biomolecular Function Simulation, RIKEN Center for Biosystems Dynamics Research, Kobe, Hyogo 650-0047, Japan
3. Theoretical Molecular Science Laboratory, RIKEN Cluster for Pioneering Research, Wako, Saitama 351-0198, Japan