1. Department of Biology/Chemistry and Center for Cellular Nanoanalytics (CellNanOs) Osnabrück University 49076 Osnabrück Germany
2. Department of Molecular and Cellular Physiology Department of Structural Biology Howard Hughes Medical Institute Stanford University School of Medicine Stanford CA 94305 USA
3. Department of Biochemistry University of Zurich Winterthurerstr. 190 Zurich 8057 Switzerland