One of the major problems when performing electron cryo-microscopy (cryo-EM) is specimen movement from beam irradiation during imaging, which results in blurred, low resolution images.

One cause of excessive specimen drift is the use of carbon foils on metal (Cu) grids, which can move up to 400Å parallel to the beam.  The UltrAuFoil^® grids were specifically developed for cryo-EM, to reduce the movement of cryo-specimens during imaging.

The UltrAufoil^® grids are a 200 or 300 mesh gold grid with a 400-500Å thick polycrystalline gold foil, which have a regular square array of micrometer-sized circular holes.

These grids are similar to Quantifoil® Grids except that the UltrAuFoil^® grids use gold foil instead of a carbon foil and are less fragile. Similar to the carbon supports, the UltrAuFoil^® grids can be made hydrophilic using low-energy plasma.

The UltrAuFoil^® grids can improve your image quality by reducing radiation-induced motion without the use of sophisticated drift correction or hardware.

Two different mesh sizes are available with three different hole patterns:

• 200 mesh grids, R 2/2
• 300 mesh grids, R 0.6/1 or R 1.2/1.3

The UltrAuFoil^® grids were designed by Drs. Lori A. Passmore and Christopher J. Russo at the Medical Research Council’s Laboratory of Molecular Biology and produced by Quantifoil^® Micro Tools.*

Advantages of UltrAuFoil^®:

• The gold foil on a gold grid prevents the foil from changing shape when the sample is cooled during preparation
• Chemically inert and biocompatible
• Less fragile than carbon foils, highly conductive, & non-oxidizing
• The grids have no expiration date, but are recommended to be used within two years
• The foil is ready to use when delivered, but can be made more hydrophilic using the PELCO easiGlow™ Glow Discharge Cleaning System
• A continuous film of carbon can be added using a standard float transfer method

Some tips on using UltrAuFoil^®:

• When setting up the beam for data collection, use a circularly symmetric beam geometry, center it over a hole with a small region of the support around the edge, and take an image of the center of the hole.
• The easiest way to focus on the grids is to minimize the image shift by using the beam tilt wobble OR remove the objective aperture and find diffracted beams at the edge of a hole, and then minimize the shift between the crystals of gold and the diffracted beams.
• For correcting the astigmatism, it is best to use a calibrated standard before imaging the sample.
• Sample collection can be automated using the beam tilt to focus.