Chameleon

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 haas 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.

Citations