1. NMR Spectroscopy Research Group Bijvoet Center for Biomolecular Research Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
2. Macromolecular Biochemistry Leiden Institute of Chemistry Leiden University Einsteinweg 55 2333 CC Leiden The Netherlands
3. Current address: NMR Spectroscopy Research Group Bijvoet Center for Biomolecular Research Utrecht University Padualaan 8 3584 CH Utrecht The Netherlands
4. Current address: DSM Food Specialties DSM Biotechnology Center Alexander Flemminglaan 1 2613 AX Delft The Netherlands