1. Divisions of Chemistry and Applied Physics, Department of Physics and Measurement Technology, Biology and Chemistry, Linköpings universitet, SE-581 83 Linköping, Sweden, Department of Organic Chemistry, Arrhenius Laboratory, Stockholms universitet, SE-106 91 Stockholm, Sweden, and Division of Clinical Bacteriology, Department of Immunology, Microbiology, Pathology and Infectious Diseases, Karolinska Institute, Huddinge University Hospital, SE-141 86 Huddinge, Sweden