1. Department of Physics; Umeå University; SE-901 87 Umeå Sweden
2. Department of Physiology and Biophysics; Boston University School of Medicine; Boston MA 02118 USA
3. The Laboratory for Molecular Infection Medicine Sweden (MIMS) and Department of Molecular Biology; Umeå University; SE-901 87 Umeå Sweden
4. Enteric Diseases Department; Infectious Diseases Directorate; Naval Medical Research Center; Silver Spring MD 20910 USA
5. Department of Pediatrics; Uniformed Services University of the Health Sciences; Bethesda MD 20814 USA