1. Ludwig-Maximilians-Universität München Department of Chemistry and Center for Integrated Protein Science CIPSM Butenandtstr. 5–13 81377 München Germany
2. Ludwig-Maximilians-Universität München Center for Integrated Protein Science CIPSM Department Biology II Planegg-Martinsried 82152 München Germany
3. Current address: Friedrich-Alexander-Universität Erlangen-Nürnberg Department of Chemistry and Pharmacy Nikolaus-Fiebiger-Str. 10 91058 Erlangen Germany