1. a Department of Chemistry , University of Nevada , Reno , NV 89557 , USA
2. b Lehrstuhl für Physikalische Chemie II , Ruhr-Universität Bochum , 44780 Bochum , Germany
3. c Departments of Chemistry and Physics , Center for Biophysics and Computational Biology , University of Illinois , Urbana , IL 61801 , USA