1. University of Kaiserslautern, Department of Physics, Erwin-Schrödinger-Strasse, 67663 Kaiserslautern, Germany, Weizmann Institute of Science, Rehovot, Israel, Max-Planck-Institute for Molecular Physiology, Dortmund, Germany, and University of Kaiserslautern, Department of Biology, Erwin-Schrödinger-Strasse, 67663 Kaiserslautern, Germany