1. Department of Chemistry Umeå University Umeå Centre for Microbial Research Umeå SE-90187 Sweden
2. Department of Chemical Biology Max Planck Institute of Molecular Physiology Otto-Hahn-Strasse 11 44227 Dortmund Germany
3. Physical Chemistry I – Biophysical Chemistry Department of Chemistry and Chemical Biology TU Dortmund University Otto-Hahn-Strasse 4a, 44227 Dortmund, Germany
4. Present address: Department of Chemical Sciences University of Naples Federico II Via Cintia 4 Naples 80126 Italy
5. Faculty of Chemistry and Chemical Biology Technical University Dortmund Otto-Hahn-Strasse 6 Dortmund 44227 Germany