Tecnai g2 t20 twin transmission electron microscope

For negative staining, 10 μL of DNA nanotube-containing solution (1 × PBS, 10 mM MgCl₂, 30 nM DNA nanotubes, and starPEG-(KA7)₄ concentrations as described) 0.1% paraformaldehyde was applied onto a glow-discharged 100 mesh copper grid with carbon-coated Formvar (Plano GmbH) and incubated for 30 min under a box. The solvent was removed by gentle blotting from one side with filter paper. The grid was rinsed with 3 drops of water, blotted again, and treated with 10 μL of 0.5% (w/v) uranyl acetate solution for 20 s. After removing the staining solution thoroughly by blotting with filter paper, the grid was air dried and imaged on a FEI Tecnai G2 T20 twin transmission electron microscope (FEI NanoPort) operated at 200 kV. Electron micrographs were acquired with an FEI Eagle 4k HS, 200 kV CCD camera at 14,500x nominal magnification.

For negative staining,
5 μL of DNA filament-containing solution (1× PBS, 10 mM
MgCl₂, 1 μM DNA filaments, 20 mg/mL dextran or 0.4
wt % MC) of 0.5% PFA was applied onto a glow-discharged 100 mesh copper
grid with carbon-coated Formvar (Plano GmbH, Wetzlar, Germany) and
removed after 2 min by gentle blotting from one side with filter paper.
The grid was rinsed with three drops of water, blotted again, and
treated with 10 μL of 0.5% (w/v) uranyl acetate solution for
20 s. After the staining solution was thoroughly removed by blotting
with filter paper, the grid was air-dried and imaged on a FEI Tecnai
G2 T20 twin transmission electron microscope (FEI NanoPort, Eindhoven,
The Netherlands) operated at 200 kV. Electron micrographs were acquired
with an FEI Eagle 4k HS, 200 kV CCD camera at 20000× nominal
magnification.