1 J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, CZ18223, Prague 8, Czech Republic.
2 Institute of Physics, Czech Academy of Sciences, Department of Radiation and Chemical Physics, Na Slovance 1999/2, CZ18221, Prague 8, Czech Republic.
3 Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, CB2 0QH, Cambridge, United Kingdom. johns@mrc-lmb.cam.ac.uk.
4 J. Heyrovský Institute of Physical Chemistry, Czech Academy of Sciences, Dolejškova 3, CZ18223, Prague 8, Czech Republic. civis@jh-inst.cas.cz.