1. Abteilung Biophysikalische Chemie, Biozentrum der Universität Basel, Klingelbergstrasse 70, CH4056 Basel, Switzerland
2. Department of Physical Biochemistry, John Curtin School of Medical Research, The Australian National University, Canberra, A.C.T. 2601, Australia
3. Department of Biochemistry, University of Oxford, South Parks Road, Oxford OXI 3QU, U.K.