1. Department of Physical Chemistry, University of Freiburg, Albertstrasse 21, 79104 Freiburg, Germany
2. Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
3. School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom
4. Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States