1. Department of Physics, Faculty of Science, University of Helsinki, P.O. Box 64, FI-00014 Helsinki, Finland
2. Theoretical Physics and Center for Biophysics, Saarland University, 66123 Saarbrücken, Germany
3. Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Kraków, Poland
4. Division of Pharmaceutical Biosciences, Drug Research Program, Faculty of Pharmacy, University of Helsinki, Viikinkaari 5 E, 00014 Helsinki, Finland