1. Department of Chemistry and Molecular Biology, University of Gothenburg, Box 462, 40530 Gothenburg, Sweden.
2. Department of Biochemistry, Radboud University Medical Center, P.O. Box 9101, 6500 HB Nijmegen, Netherlands.
3. Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
4. Laboratory of Biomolecular Research, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.
5. Department of Biology, ETH Zürich, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland.
6. Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland.