1. Drittes Physikalisches Institut–Biophysik, Georg-August-Universität, 37077 Göttingen, Germany.
2. Department of Chemical and Biomolecular Engineering, Department of Chemistry, Smalley Institute for Nanoscale Science and Technology, Rice University, Houston, TX 77005, USA.
3. Department of Physics and Astronomy, Vrije Universiteit, 1081 HV Amsterdam, Netherlands.