1. Institute of Molecular Physiology, Johannes Gutenberg University Mainz, Johannes-von-Müller-Weg 6, 55128 Mainz, Germany
2. Institute of Physical Chemistry, University of Goettingen, Tammannstrasse 6, 37077 Goettingen, Germany
3. Microscopy Core Facility, Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany