1. Department of Applied Physics, Helsinki University of Technology, Finland, Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi Prospect 31, V.O., St. Petersburg, 199004 Russia, Department of Physics, Tampere University of Technology, Finland, MEMPHYS-Center for Biomembrane Physics, University of Southern Denmark, Denmark, and Department of Applied Mathematics, The University of Western Ontario, London, Ontario, Canada