1. Laboratory of Biophysics, Wageningen University, P.O. Box 8128, 6700 ET, Wageningen, The Netherlands
2. Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, VU University, DeBoelelaan1081, 1081 HV Amsterdam, The Netherlands
3. Commissariat à l’Energie Atomique, Institut de Biologie et Technologies de Saclay and Centre National de la Recherche Scientifique, 91191 Gif sur Yvette, France
4. MicroSpectroscopy Centre, Wageningen University, P.O. Box 8128, 6700 ET, Wageningen, The Netherlands