1. Faculty of Physics and Center for Nanointegration Duisburg−Essen (CENIDE), University of Duisburg−Essen, Lotharstraße 1, Duisburg D-47057, Germany
2. Institute of Physical Chemistry, Chemistry Department, Faculty of Mathematics and Natural Sciences, University of Cologne, Luxemburger Straße 116, Cologne D-50939, Germany
3. Institute for Complex Systems, IHRS BioSoft, Forschungszentrum Jülich GmbH, Jülich D-52428, Germany