1. Laboratory of Physical Chemistry and Soft Matter; Wageningen University and Research Centre; Wageningen 6703HB The Netherlands
2. Simpson Querrey Institute for BioNanotechnology; Northwestern University; Chicago Illinois 60611-2875 USA
3. Laboratory of Bionanotechnology; Wageningen University and Research Centre; Wageningen 6703HB The Netherlands
4. Wageningen Electron Microscopy Centre; Wageningen University and Research Centre; Droevendaalsesteeg 1 6708 PB Wageningen The Netherlands