The introduction of direct electron detectors dramatically enhanced the signal-to-noise ratio of electron micrographs, resulting in a marked improvement in the quality of cryo-electron microscopy (EM) reconstructions (known as the "resolution revolution").
This approach and developments in image processing and data collection have increased the resolution of single-particle cryo-EM reconstructions to the point that the electron source may become a limiting factor.
This has resulted in a rethinking of cryo-EM alternatives to the traditional Schottky field emission gun (FEG), such as the cold FEG, due to their greater coherence.
Despite the acknowledged advantages of cold FEG over thermally aided FEG, practical constraints prohibited its application in cryo-EM until JEOL's CryoARM microscope series was developed.
Cold FEG was first utilized on 300 kV cryomicroscopes to test the limits of attainable resolution, eventually culminating in cryo-EM reconstructions at "atomic resolution," which shows individual atoms as isolated spheres of density.
Following this achievement, attempts have been made to use the cold FEG source on 200 kV cryomicroscopes, which are typically smaller and less expensive, to test how far the tighter energy distribution could push the resolution on this more accessible instrument.
This webinar will discuss results from a cold FEG-equipped CryoARM200 microscope, demonstrating how 200 kV data can be exploited to build sub-2Å structures for various samples.
The resolution of the reconstructions is equivalent to that of more expensive high-end 300 kV microscopes.
The results reported in the webinar are based on automated data collection using the open-source program SerialEM.
Many users are familiar with SerialEM, and its openness and ease of use make obtaining high-quality data on this platform achievable even for those without expertise using a CryoARM microscope.
Image Credit: JEOL USA, Inc.
About the Presenters
Alan Merk, Electron Microscopist at Leidos Biomedical Research
Alan worked as a microscopist in Sriram Subramaniam's group at the Center for Cancer Research, NCI, for eight years, creating methods for high-resolution data collecting on a 300 kV Titan Krios.
Alan then joined Jana Ognjenovic's group at the Frederick National Laboratory, where he seeks to push the resolution limits of 200 kV microscopes, notably a CryoARM200.