1. Department of Structural
Biology, Max-Planck-Institute of Biophysics, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany
2. Department of Chemistry, Philipps-University of Marburg, Hans-Meerwein-Str. Bldg. H, D-35032 Marburg,
Germany
3. Material Sciences Center, D-35032 Marburg, Germany