1. Technische Universität Braunschweig Institute of Organic Chemistry Hagenring 30 38106 Braunschweig Germany
2. Institute of Physical Chemistry RWTH Aachen University Melatener Str. 20 52056 Aachen Germany
3. Department of Biochemistry The University of Texas Southwestern Medical Center 5323 Harry Hines Boulevard Dallas TX 75390-9038 USA
4. Technische Universität Braunschweig Institute of Inorganic and Analytical Chemistry Hagenring 30 38106 Braunschweig Germany