vitrification system was
used to prepare the samples for cryo-TEM measurements. Humidity was
kept close to 80% for all experiments and the ambient temperature
was 295 K. Aliquots (3 μL) of each sample were pipetted onto
a 300-mesh copper grid coated with lacey Formvar over a perforated
carbon support (ProSciTech, Thurwingowa, Australia GSCu300FL-50C)
that were glow discharged in nitrogen to render them hydrophilic.
After ∼10 s adsorption time the grid was blotted manually with
Whatman 541 filter paper for ∼2 s. Blotting time was optimized
for each sample. The grid was then plunged into liquid ethane cooled
by liquid nitrogen. Frozen grids were stored in liquid nitrogen until
the cryo-TEM measurements were performed. The samples were examined
using a Gatan 626 cryoholder (Gatan, Pleasanton, CA) and Tecnai 12
Transmission Electron Microscope (FEI, Eindhoven, The Netherlands)
at an operating voltage of 120 kV. At all times, low dose procedures
were followed using an electron dose of 8–10 electrons Å–2. Images were recorded using a Megaview III CCD camera
and AnalySIS camera control software (Olympus). Consistent images
were observed in at least three independent grid squares.