1. Max-Planck Institute of Molecular Physiology Otto-Hahn Strasse 11 44227 Dortmund Germany
2. Current address: School of Physical and Chemical Sciences University of Canterbury Private Bag 4800 Christchurch 8140 New Zealand
3. Current address: Department of Chemistry Technical University of Denmark, kemitorvet 207 2800 Kgs. Lyngby Denmark
4. Faculty of Chemistry and Chemical Biology TU Dortmund University Otto-Hahn Strasse 4a 44227 Dortmund Germany