Next generation sample preparation for CryoEM
Chameleon is a blot-free, pico-liter sample vitrification instrument that aims to minimize detrimental air-water interface effects for challenging biological samples, while addressing the need for robust, automated cryoEM sample preparation. The full commercial version of chameleon will be available at our Woburn location starting in January, 2021, and will be available in all CryoEM Starter Programs.
- blot-free, high-speed plunging reduce air-water interface effects and enable difficult samples
- easy to use even for novice users
guided workflows enables simple set up, use and cleaning
- record keeping for future repeatability
capture all relevant grid parameters and images
- screen fewer grids at the microscope
select good grids based on visual images during freezing
- virtually no manual handling
eliminate damage and loss via precise automated grid handling
- safe storage and control of cryogen
automated drawer offers level sensing and temperature control
The Chameleon Story
Chameleon is a commercial development of the successful 'Spotiton' system, a decade-long project by NIS founders Bridget Carragher and Clint Potter. Realizing the limitations of existing grid preparation practices, they set out to develop a robust and repeatable technique for specimen vitrification based on small volume dispensing using inkjet technology.
First published in 2012, Spotiton has enabled high resolution structure determination for numerous structures, as well as contributed significantly to the understanding of protein behavior at the air-water interface. Arriving at NIS in January 2020, the fully equipped Chameleon distills out the advantages of Spotiton and builds on proven knowledge of process automation in the field of structural biology.
Overcoming challenges resulting from the effects of air-water interface
Producing quality frozen grids with vitreous ice of an appropriate thickness and evenly distributed particles remains one of the major bottlenecks in the structure determination process. Most protein particles prepared in vitreous ice for single-particle cryo-electron microscopy (cryoEM) are adsorbed to one or both of the air-water interfaces, which can cause the particles to adopt preferred orientations. It can be difficult to generate a 3D map if most particles are in the same orientation.
By using a rapid plunge-freezing robot and nanowire grids, chameleon reduces the effects of the air–water interface by decreasing the time particles have to move toward the air-water interface before freezing. More sample remains floating in random orientations in solution. This approach also minimizes protein aggregation and the dissociation of multi-component complexes during vitrification.
Fixing issues with sample waste and damage
Traditional sample preparation involves injecting 3 uL of sample onto a grid and then pressing the grid between two pieces of blotting paper. The blotting paper removes 99.9% of the sample, leaving a tiny amount of sample on the grid. The thin layer of sample remaining on the grid can often be too thick, too thin, or damaged from the brute force of the blotting method.
Chameleon uses a piezoelectric dispensing device that sprays a 50 pL sample directly onto the grid, conserving the amount of sample used while avoiding the brute force of the blotting step all together. A rapid plunge-freezing robot sends the grid past the dispenser while it is spraying the 50 pL sample. Self-blotting nanowire grids, together with a patterned holey carbon film, allow the sample to spread out into a thin, even distribution of particles.
Chameleon demo video by SPT Labtech
See how it works in real life at our NIS-East Client Center in Woburn, MA, starting in January 2020.
- Noble AJ, et al. Routine single particle CryoEM sample and grid characterization by tomography. Elife. 2018;7. https://doi.org/10.7554/eLife.34257
- Noble AJ, et al. Reducing effects of particle absorption to the air-water interface in cyo-EM. Elife. Nat Methods. 2018; 15 (10):793-5. https://doi.org/10.1038/s41592-018-0139-3
- Dandey VP, Wei H, Zhang Z, Tan YZ, Acharya P, Eng ET, Rice WJ, Kahn PA, Potter CS, Carragher B. Spotiton: New features and applications. J Struct Biol. 2018 May;202(2):161-169.
- Wei H, Dandey VP, Zhang Z, Raczkowski A, Rice WJ, Carragher B, Potter CS. Optimizing "self-wicking" nanowire grids. J Struct Biol. 2018 May;202(2):170-4.