Grids for Calibration¶

The grid used for calibration should have reasonable contrast and features at multiple
scale. A frozen grid is generally not convenient for the purpose since the contrast is low and
can drift easily. Large protein complex negatively stained on a 200-400 mesh em grid with
Quantifoil, C-falt, or home-made holey carbon support is ideal. You can even use one that is
abandoned after a cryo run, just negatively stain it to improve the contrast. From our
experience, small protein negatively stained on continuous carbon support oftern gives low
contrast at intermediate magnification and therefore not ideal. If your Quantifoil or C-flat
grid is too clean, there may be a problem of false peaks from the lattice. In this case, you
can add some gold clusters such as Nanogold from Nanoprobe.

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