1. Center for Biomolecular Magnetic Resonance (BMRZ) Institute for Organic Chemistry and Chemical Biology Goethe University Max-von-Laue-Str. 7 60438 Frankfurt/M. Germany
2. National Centre for Biomolecular Research Masaryk University Kamenice 5 625 00 Brno Czech Republic
3. Central European Institute of Technology (CEITEC) Masaryk University Kamenice 753/5 625 00 Brno Czech Republic
4. Institute of Biophysics Czech Academy of Sciences Kralovopolska 135 612 65 Brno Czech Republic
5. Present address: Center for Molecular Medicine Cologne Robert-Koch-Str. 21 50931 Cologne Germany
6. Center for Biomolecular Magnetic Resonance (BMRZ) Institute of Biophysical Chemistry Goethe University Max-von-Laue-Str. 9 60438 Frankfurt/M. Germany