1. Department of Physics, Simon Fraser University, 8888 University Drive, Burnaby, BC, Canada V5A 1S6
2. School of Chemistry, University of Bristol, Bristol BS8 1TS, UK
3. School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
4. School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
5. Centre for Applied Medical Research, St. Vincent's Hospital, Darlinghurst, Sydney, NSW 2010, Australia
6. The Nanometer Structure Consortium (nmC@LU) and Division of Solid State Physics, Lund University, Box 118, 22100 Lund, Sweden
7. Molecular Biophysics, Utrecht University, Postbus 80'000, 3508 TA Utrecht, The Netherlands