High-resolution cryo-EM using a common LaB6 120-keV electron microscope equipped with a sub-200-keV direct electron detector

Hariprasad Venugopal; Jesse Mobbs; Cyntia Taveneau; Daniel R Fox; Ziva Vuckovic; Sahil Gulati; Gavin Knott; Rhys Grinter; David Thal; Stephen Mick; Cory Czarnik; Georg Ramm

doi:10.1126/sciadv.adr0438

High-resolution cryo-EM using a common LaB₆ 120-keV electron microscope equipped with a sub-200-keV direct electron detector

Sci Adv. 2025 Jan 3;11(1):eadr0438. doi: 10.1126/sciadv.adr0438. Epub 2025 Jan 3.

Authors

Hariprasad Venugopal¹, Jesse Mobbs^{2

3}, Cyntia Taveneau⁴, Daniel R Fox^{3

5

6}, Ziva Vuckovic⁴, Sahil Gulati⁷, Gavin Knott⁸, Rhys Grinter^{3

5

6}, David Thal^{2

3}, Stephen Mick⁷, Cory Czarnik⁷, Georg Ramm^{1

8}

Affiliations

¹ Ramaciotti Centre for Cryo-Electron Microscopy, Monash University, Clayton, VIC, Australia.
² Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia.
³ Australian Research Council Centre for Cryo-Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, VIC, Australia.
⁴ GlycoEra AG, Einsiedlerstrasse 34, 8820 Wädenswil, Switzerland.
⁵ Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia.
⁶ Department of Biochemistry and Pharmacology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Parkville, VIC, Australia.
⁷ Gatan Inc., Pleasanton, CA, USA.
⁸ Department of Biochemistry and Molecular Biology, Monash Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia.

Abstract

High-resolution cryo-electron microscopy (cryo-EM) requires costly 200- to 300-keV cryo-transmission electron microscopes (cryo-TEMs) with field emission gun (FEG) sources, stable columns, constant-powered lenses, autoloader, and direct electron detectors (DED). Recent advances in 100-keV imaging with the emergence of sub-200-keV optimized DED technology promises the development of more affordable cryo-TEMs. So far, 100-keV imaging has required microscopes with FEG sources. We here explored whether a standard 120-keV TEMs with thermionic lanthanum hexaboride (LaB₆) source can be upgraded with a sub-200-keV DED for high-resolution cryo-EM. Using this imaging configuration, we successfully obtained a 2.65 Å reconstruction for apoferritin, 4.33 Å for 64-kDa hemoglobin, and 4.4 Å for an asymmetric 153kDa membrane protein GPCR. All results were achieved using standard automated data collection with SerialEM, demonstrating the feasibility to collect large cryo-EM datasets with a side-entry cryo-holder. These results showcase a widely accessible solution to obtaining interpretable cryo-EM structures at low cost and contribute to the "democratization" of cryo-EM.