1. IFM-Laboratory of Applied Physics and IFM-Department of Chemistry, Linköping University, S-581 83 Linköping, Sweden, Department of Biochemistry, Umeå University, S-901 87 Umeå, Sweden , Department of Thermochemistry, University of Lund, S-221 00 Lund, Sweden, and Department of Cell and Molecular Biology, Interface Biophysics, Göteborg University, S-413 90 Göteborg, Sweden