QUANTIFOIL®

QUANTIFOIL is a perforated support foil with pre-defined hole size, shape and arrangement. It has advantages in electron microscopy (EM) or low-energy electron point source (LEEPS) microscopy when compared with conventional holey film.

QUANTIFOIL is offered with circular and square, orthogonal arranged holes. Films with different hole sizes and bar widths are available. Carbon is the standard material that makes the foil but gold and SiO₂ is also available.

General Information:

1. Hole Size:
Refers to the diameter of the individual holes in the film. The hole size determines how much of the sample is unsupported and visible through the grid, which is crucial for applications like cryo-electron microscopy (cryo-EM), where the sample sits in the holes for optimal imaging.

2. Spacing:
This is the distance between the centres of adjacent holes in the QUANTIFOIL film. Spacing affects how densely the holes are packed across the film and, consequently, the distribution of the sample on the grid.

3. Period:
This refers to the repeating pattern of holes across the grid film. It is defined by the combined length of the hole and the surrounding film that separates each hole, creating a repeating lattice structure.

QUANTIFOIL HexAuFoil^®

SPT Labtech are now scaling up full production of HexAuFoil® ultra-small hole gold-on-gold grids. Developed at the MRC Laboratory of Molecular Biology, Cambridge, UK and requiring a completely novel production process to deliver the dense array of 300 nm holes, these grids offer:Virtually movement-free imaging.

• Consistent, thin (approx 35nm) ice across 9m holes on each grid.
• The possibility of zero dose reconstructions for the first time.
• Improved stability, less re-focusing and faster data collections, due to their dense, hexagonal design.
• An ideal solution for cryo-EM scientists in industry or academia looking to maximise output of high-quality reconstructions for SBDD and academic research.

These grids are a pre-production version supplied by SPT Labtech, they may differ in their detailed appearance from the final product which will be available on the website soon. Despite these differences, they will still deliver the expected benefits of the HexAuFoil^® technology, including consistently thin ice that enables the virtual elimination of beam-induced particle motion.

QUANTIFOIL^® Holey Carbon Support

Holey Carbon supports are a flat film of carbon, 10-12 nm thick, on a cryo-electron microscopy (cryo-EM) grid. They provide a low-background sample support ideal for high-resolution cryo-EM data collection. The optimum grid for your project can be selected from a wide variety of hole shapes, sizes and spacings in combination with a range of base grid materials and mesh sizes. Grid options include standard square meshes as well as other arrangements and finder grid formats.

Circular - Ideal for high-resolution studies of biological macromolecules and other materials, round holes optimise the formation of a thin, even layer of ice to support a sample of interest. Select from our wide range of geometries depending on the characteristics of your sample and your imaging modality.

Square - Often used for applications where larger carbon-free areas are desired, square grids have less carbon support. They can be used with an additional thin carbon layer where samples need continuous support.

Multi A - With a repeating pattern of hole size, shape and spacing, Multi A foils are useful for particles of unpredictable size, for example liposomes, while the oval shape can aid in tomographic data collection.

HOW TO PREPARE HOLEY CARBON FILM SUPPORTS

QUANTIFOIL^® UltrAuFoil

Better 3D reconstructions from less data with ultra-stable gold supports for cryo-electron microscopy that reduce the movement of frozen specimens during imaging.

Designed at MRC's Laboratory of Molecular Biology by Dr Christopher J Russo and Dr Lori A Passmore and manufactured exclusively under license by Quantifoil Micro Tools GmbH1, UltrAuFoil® Holey Gold sample supports make structure determination for challenging and small molecules easier.

During imaging at cryogenic temperatures, traditional carbon supports move, particularly at the beginning of irradiation. This movement blurs images and reduces data quality. UltrAuFoil® Holey Gold supports are more conductive, and there is no differential contraction between the grid and the foil on plunge freezing. Therefore, there is less crinkling of the foil during sample preparation, resulting in many improvements in data quality.

UltrAuFoil® Gold supports for better reconstructions with less data

• Increases resolution, by up to 0.5 Å when replacing traditional holey carbon supports with UltrAuFoil®.
• Reduces image distortion from the accumulation of static and semi-mobile charge as gold is highly conductive at liquid nitrogen temperatures.
• Protects samples from damage due to accumulating positive charge by neutralising it with secondary electrons generated by irradiating adjacent gold.
• Allows biomolecules to retain native structure and by not putting them under mechanical strain from foil crinkling.
• Improves particle distribution as the gold foil is even flatter than carbon, and capable of forming the <200 Å ice layers required for ultra-high resolution data collection on smaller molecules.
• Simplifies grid surveying due to the high contrast of the gold foil.

Additional Ultrathin Continuous Carbon Layer

Particle density and distribution has been widely shown to improve on the addition of an ultrathin (2-3nm) carbon (UTC) layer to a grid. Data quality has improved for both QUANTIFOIL 4 Holey Carbon Films and UltrAuFoil 5 Gold Supports when a UTC layer is applied.

An additional UTC layer can be added to most QUANTIFOIL Holey Carbon Film supports on request. The most popular thickness is 2nm, but thicker, more stable, 3 and 5nm layers are also available, and even 10nm is possible. For an additional UTC on QUANTIFOIL Holey Carbon Film supports, please request a quote. Alternatively, if you are interested in adding a UTC layer to UltrAuFoil Holey Gold supports, please contact us for further details.

PLEASE NOTE - As the ultrathin carbon layer may not be as stable as our usual films, we recommend using grids with a UTC layer within 6 months of delivery.

Improvements in specimen quality

Shown in the image is the structure of Photorhabdus luminescens TcdA1, a large multisubunit complex toxin, with activity against insects, whose structure was determined using images collected on QUANTIFOIL® R 2/1 grids with a 2nm additional carbon layer6. Many biomolecules have a strong affinity for carbon, and a number of factors contribute to a resulting improvement in specimen quality:

• Increased numbers of particles due to adsorption of biomolecules onto carbon prior to blotting.
• Improved particle distribution due to interaction with carbon surface across the hole.
• Reduction in the number of particles adopting a preferred orientation.

QUANTIFOIL^® SiO₂ Films

Methods development for in situ structural investigation by FIB-milling and cryo-electron tomography

• Toro-Nahuelpan et al. Tailoring cryo-electron microscopy grids by photo-micropatterning for in-cell structural studies. Nat Methods 17: 50-54 (2020)
• Lucas and Grigorieff. Quantification of gallium cryo-FIB milling damage in biological lamellae. Proc. Natl Acad. Sci. USA 120: e2301852120 (2023)
• Franken et al. Protocol for live-cell fluorescence-guided cryoFIB-milling and electron cryo-tomography of virus-infected cells. STAR Protocols 3: 101696 (2022)

Recent examples of Cryo-ET investigations using SiO₂ grids

1. Shepherd et al. Throughput-scalable manufacturing of SARS-CoV-2 mRNA lipid nanoparticle vaccines. Proc Natl Acad Sci USA 120: e2303567120 (2023)
2. Winter et al. The Ebola virus VP40 matrix layer undergoes endosomal disassembly essential for membrane fusion. EMBO J 42: e113578 (2023)
3. Zhang et al. Molecular mechanisms of stress-induced reactivation in mumps virus condensates. Cell 186: 1877-1894 (2023)

QUANTIFOIL^® Active

Self-wicking grids for use exclusively with SPT Labtech chameleon.

QUANTIFOIL® Active grids are unique in being the first commercially produced grids with copper nano-wire covered bars to promote thin film formation through a process of “self-wicking”. Brought to you in collaboration with our sister company SPT Labtech, these supports eliminate the variability of using an externally applied filter paper to remove excess sample during blotting.

Only for use in single particle cryo-EM studies with the SPT Labtech chameleon: Automatic sample preparation with chameleon streamlines cryo-EM workflows with high speed blot-free vitrification, automated grid handling, and the ability to screen grids based on likely ice thickness.