1. Institute of Organic Chemistry and Biochemistry, v.v.i., Academy of Sciences of the Czech Republic, Flemingovo Square 2, 166 10 Prague 6, Czech Republic, Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, Scheikundig Laboratorium der Vrije Universiteit, De Boelelaan 1083, NL-1081 HV Amsterdam, The Netherlands, and Institute of Biophysics, v.v.i., Academy of Sciences of the Czech Republic, Královopolská 135, 612 65 Brno, Czech Republic