1. Computational Molecular Biophysics, IWR, University of Heidelberg, Im Neuenheimer Feld 368, 69120 Heidelberg, Germany, Institute of Pharmacy and Molecular Biotechnology, University of Heidelberg, Im Neuenheimer Feld 364, 69120 Heidelberg, Germany, and Oak Ridge National Laboratory, Post Office Box 2008 MS 6309, Oak Ridge, Tennessee 37831-6309