1. Faculty of Sciences, Division of Physics and Astronomy, Department of Biophysics and Physics of Complex Systems, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow G128QQ, United Kingdom, and Laboratory of Biophysics, Department of Agrotechnology and Food Sciences, Dreijenlaan 3, 6703 HA Wageningen, The Netherlands.