1. Institute of Cell Biology, University of Bern 1 , Bern, Switzerland
2. Graduate School for Cellular and Biomedical Sciences, University of Bern 2 , Bern, Switzerland
3. Drexel University 3 Department of Electrical and Computer Engineering, , Philadelphia, PA, USA
4. Institute for Biology, Karl-Franzens-University Graz 4 , Graz, Austria