1. Department of New Materials and Biosystems, Max-Planck-Institute for Metals Research, Heisenbergstrasse 3, 70569 Stuttgart, Germany, Department of Biophysical Chemistry, The University of Heidelberg, INF 253, 69120 Heidelberg, Germany, the Department of Biological Chemistry, John Innes Centre, Colney, Norwich NR4 7UH, United Kingdom, and Q-Sense AB, Redegatan 13, 42677 Västra Frölunda, Sweden