1. Department of Chemistry University of Zurich Winterthurerstrasse 190 CH-8057 Zurich Switzerland
2. Institute of Biophysical Chemistry Center for Biomolecular Magnetic Resonance Goethe University Frankfurt Max-von-Laue-Straße 9 60438 Frankfurt am Main Germany
3. Institute of Organic Chemistry and Chemical Biology Goethe University Frankfurt Max-von-Laue-Straße 7 60438 Frankfurt am Main Germany
4. Laboratory of Physical Chemistry ETH Zürich Vladimir-Prelog-Weg 2 8093 Zurich Switzerland