Thermo Scientific Glacios Cryo-TEM
CEMAS offers access to a comprehensive suite of instruments needed for cryo-electron microscopy (cryoEM) research that encompasses the entire workflow from sample preparation to data analysis. This powerful technique allows for the observation of biological specimens in their native environment by embedding the samples in vitreous ice. Recent advances in camera technology and data processing have made it possible to determine molecular structures at near-atomic resolution. CryoEM has transformed structural biology, and its use is expanding into other fields such as small molecule crystallography, infectious disease, and cell biology.
In late 2018, CEMAS installed the Thermo Glacios cryoEM which has a 200 kV x-FEG source and can be configured for single particle analysis (SPA), tomography, and other applications.
Glacios capabilities include:
Sample screening and data acquisition
The Glacios cryoEM is the ideal microscope for screening, prior to transfer of samples to the Krios G3i for ultimate-resolution data acquisition. While it is considered a screening microscope, our Glacios is configured with a direct electron detector making it a standalone SPA data acquisition solution. In addition, the Glacios can be used to characterize the size and shape of biological samples or soft materials (such as lipids or polymers) under physiological conditions.
With full control of the Autoloader, a robotic sample handler, all 12 grids in an Autoloader cassette can be batch-screened. This screening process involves collecting a low magnification grid atlas and determining ice quality (presence, thickness) of the vitrified grids. This information can then be utilized to support the guided selection of grid squares.
Direct electron detector
The Falcon 3EC 200 kV allows for the direct detection of electrons in low-dose imaging applications dedicated to a 200 kV TEM. Its sensitivity has been increased by further backthinning of the sensor. As a result, the DQE in integrating mode has increased significantly at 200 kV (DQE @ 1/2 Nq in integrating mode: ≥ 0.3).
Falcon 3EC 200 kV is fully integrated in the Thermo Fisher architecture and dedicated protection software prevents over-exposure and ensures that the camera for direct detection is only illuminated under low-dose conditions. A Ceta 16M is part of the microscope configuration and used for surveying the specimen and performing alignments.
Microcrystal electron diffraction (MicroED)
CEMAS has upgraded the Glacios with the MicroED package offered by Thermo Fisher Scientific, which includes the Ceta-D camera upgrade along with additional apertures, a modified beamstop, and EPU-D data collection software. The Ceta-D features a scintillator that has been optimized for low dose diffraction experiments. This camera modification has two main effects: (1) reduces noise levels by a factor of 5/increases SNR and (2) improves the DQE(0) by 1.5. Currently, CEMAS staff is working to validate the MicroED workflow for small molecule and protein crystals.
Enhanced ease-of-use through automation
The EPU software has been further streamlined to become the single user interface for the SPA workflow, providing comprehensive user guidance, as well as access to automated routines for regularly recurring alignments.