1. Institute for Biophysical Chemistry; Medizinische Hochschule Hannover; Carl-Neuberg-Strasse 1 30625 Hannover Germany
2. Division for Structural Analysis; Medizinische Hochschule Hannover; Carl-Neuberg-Strasse 1 30625 Hannover Germany
3. School of Biosciences; University of Kent; Canterbury Kent CT2 7NJ UK