1. Paul Scherrer Institute, Institute for Medical Radiobiology, 5232 Villigen-PSI, Switzerland and ICRF Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK
2. ICRF Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK and Wohl Virion Centre, The Windeyer Institute of Medical Sciences, University College London, London WIT 4JF, UK
3. Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
4. Institut für Medizinische Genetik, Universität Zürich, 8001 Zürich, Switzerland
5. Paul Scherrer Institute, Institute for Medical Radiobiology, 5232 Villigen-PSI, Switzerland
6. ICRF Clare Hall Laboratories, South Mimms, Herts EN6 3LD, UK