QUANTIFOIL® Holey Carbon Film supports with circular holes are used in a wide range of applications from materials science to molecular biology and biomedical imaging. The circular holes allow improved sample distribution and reduced background scatter due to the formation of thin, even layers of vitrified ice that support the particles of interest. Users can select from a wide range of holes depending on their sample characteristics and imaging modality:

• Small holes for high-resolution SPA of protein complexes;

• Larger holes and less carbon to maximise open viewing area for tomography and materials science;

• More Carbon and fewer holes for on-grid cell growth.

Choosing the right film for your application

The optimum base grid mesh and QUANTIFOIL® Holey Carbon Film support geometry for a particular project depends on many variables, and researchers will want to try several combinations when starting a new project. Some general guidelines when identifying the ideal film geometry for your experiment include:

Magnification

Higher magnifications require smaller holes, as the presence of some support film in the image will aid focusing. The power spectrum of the amorphous carbon is much stronger than that of ice, which allows Thon rings to be more easily seen.

As a rough guide:

• Use 1.2 μm holes and smaller (R 1.2/1.3 and R 1/1) at x 50,000 or higher magnification. These magnifications are normally used for high-resolution data collection for biological specimens.

• Approx. 2 μm holes (e.g. R 2/1 or R 2/2) for x 30,000 and x 40,000

• 5 μm or larger (e.g. R 8/3 or R 6/6.5) at x 20,000

Sample

A larger sample size will require larger hole sizes. For example:

• Proteins and protein complexes at high-resolution: R 1.2/1.3 or R 0.6/1
  

• Viruses and tomography: R 2/1, R 2/2, R 2/4

• Fibrils and other extended structures: R 3.5/1

• Whole cells often need additional support, with holes more widely spaced: R 2/2, R 2/4, R 1/4, R 1.2/20

Application

• Tomographic applications often benefit from larger open viewing areas due to tilting of the grid, so select smaller intervals between holes such as R 3.5/1

• To increase data collection speed using beam-image shift, choose a larger hole size (R 2/1 or R 2/2), to allow multiple shots in the same hole before shifting the stage and re-focusing.