1. Division of Molecular Biosciences,
Faculty of Natural Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, U.K.
2. Department of Medical Biochemistry,
Academic Medical Center, University of Amsterdam, Meibergdreef 15, 1105 AZ Amsterdam, The Netherlands
3. Biomolecular Analysis and Spectroscopy,
LaserLab, Vrije Universiteit Amsterdam,
De Boelelaan 1081, 1081 HV, The Netherlands