1. Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K.
2. School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, U.K.
3. Department of Chemical Physics, Faculty of Mathematics and Physics, Charles University, Prague 121 16, Czech Republic
4. Faculty of Science, University of South Bohemia, Ceske Budejovice 370 05, Czech Republic
5. School of Physics and Astronomy, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds LS2 9JT, U.K.