1 Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic.
2 Laboratory of Biophysics, Wageningen University, Wageningen, The Netherlands.
3 MicroSpectroscopy Research Facility, Wageningen University, Wageningen, The Netherlands.
4 Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic.
5 Biology Centre, Czech Academy of Science, České Budějovice, Czech Republic.
6 Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Prague, Czech Republic. psencik@karlov.mff.cuni.cz.