1. Department of Soft Matter Chemistry, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Culgi B.V., P.O. Box 252, 2300 AG Leiden, The Netherlands, and Soft Matter cryoTEM Research Unit, Department of Biomedical Engineering, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands