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 Laboratoire de Bioimagerie et Pathologies, UMR7021 CNRS, Faculté de Pharmacie, Université de Strasbourg, Cedex, 67401 Illkirch, France.