1. Center for Molecular Biophysics, University of Tennessee/Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831, Research Program for Computational Science, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan, and Computational Molecular Biophysics, Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer Feld 368, Heidelberg 69120, Germany