1. Department of Organic Chemistry, Stockholm University, 10691 Stockholm, Sweden
2. Structural Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden
3. Department of Chemistry, School of Chemical Science and Engineering, Royal Institute of Technology (KTH), 10044 Stockholm, Sweden
4. Biophysics Group, Department of Chemistry, University of Gothenburg, P. O. Box 462, 40530 Gothenburg, Sweden