1. Department of Sciences, University College Groningen, University of Groningen, 9718 BG Groningen, The Netherlands
2. Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, United States
3. Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
4. Laboratory of Computational Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States