1. Computational Molecular Biophysics, Interdisciplinary Center for Scientific Computing (IWR), Im Neuenheimer Feld 368, Universität Heidelberg, 69120 Heidelberg, Germany, Structural Biology and Bioinformatics, University of Bayreuth, Universitätsstrasse 30, Gebäude B14, 95447 Bayreuth, Germany, and Oak Ridge National Laboratory and Center for Molecular Biophysics, University of Tennessee, 1 Bethel Valley Road, Oak Ridge, Tennessee 37831