1. Department of Structural Biology, Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands, Division of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands, and Laboratory of Biophysics, Department of Agrotechnology and Food Sciences, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands