1. Institute of Physics of the CAS, Na Slovance 2, 182 21 Prague, Czech Republic
2. Department of Biochemistry and Microbiology, University of Chemistry and Technology Prague, Technická 3, 16628 Prague, Czech Republic
3. J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3, 182 23 Prague, Czech Republic