1 The Photophysics Research Group, University of Strathclyde, Department of Physics, SUPA, John Anderson Building, 107 Rottenrow, Glasgow, G4 0NG, United Kingdom.
2 School of Molecular Sciences and The Biodesign Institute, Arizona State University, PO Box 875601, Tempe AZ, 85287-5601, United States of America.
3 UMR 7021 CNRS, Laboratoire de Bioimagerie et Pathologies, Faculté de Pharmacie, 74 route du Rhin, F - 67401 Illkirch, France.