1. Division of Physical Chemistry, Chemistry Department, Lund University, P.O. Box 124, 22100 Lund, Sweden
2. Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
3. Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Am Mühlenberg 1, 14476 Potsdam, Germany