Low-Energy Cryo-EM to Improve the Accessibility of Fast and Accurate Structure Determination

A 5-minute read

A purpose-built electron cryo-microscope, running at 100 keV, promises to reduce the cost and complexity of studies on biological structures.

Though electron cryo-microscopy (cryo-EM) has proved to be an invaluable technique for obtaining detailed atomic structures of biological materials, technological advancements have steadily propelled its costs upwards. Current state-of-the-art microscopes now cost several million dollars, precluding many researchers and institutes from using this beneficial approach, and this obstacle ultimately slows down progress toward molecular discoveries. To combat this, Chris Russo’s group and Richard Henderson, both in the LMB’s Structural Studies Division, have worked with a team across the LMB – as well as industrial partners at JEOL UK, York Probe Sources, and DECTRIS – to build a new microscope at a fraction of the size and costs utilized by current suppliers.

The spiraling costs of electron microscopes are largely due to the systematic rise in electron energies to combat issues such as poor electron detector efficiency, low source brightness, ice contamination, and more. However, previous research from Chris’ group has illustrated that 100 thousand electron volts (keV) – three times lower than the current most popular energy of 300 keV – is actually the optimal energy for imaging of thin specimens.

Spearheaded by Greg McMullan, the team built a new electron microscope, eschewing some recent additions that drive up costs. The new microscope features several bespoke features designed to optimize structure determination at a lower energy. These include a new 100-keV field emission gun from York Probe Sources; a JEOL low-aberration objective lens with a cryobox; and a new SINGLA high-speed, high-efficiency electron detector from DECTRIS.

To prove its capabilities, a team of researchers including Ph.D. students and postdocs, used the new microscope to determine eleven atomic structures. The macromolecular specimens chosen were a diverse selection, with varying sizes and symmetries and a range of subunit numbers from one to sixty. Notably, each was solved with a fraction of the data that are normally required, with each structure being obtained after a single day of manual data collection.

This new electron microscope promises to increase the accessibility of cryo-EM significantly. Not only does the microscope cost up to ten times less than current high-end models – while delivering similar results for single-particle cryo-EM – but the additional costs of establishing a microscopy room are also reduced tenfold, and running costs are at just 5% of current levels. Ultimately, this will encourage faster scientific progress, allowing research laboratories around the world to access quick, simple, and reliable cryo-EM – which is a key technique for many scientific studies, including the process of developing new drugs.

This breakthrough builds on the LMB’s long history at the forefront of cryo-EM development. Its innovations range from using Electron Microscopy to determine the structure of 2-D crystals of the membrane protein bacteriorhodopsin in the 1970s, to the adoption and development of cryo-EM in the 1980s and 1990s, to the more recent achievement of atomic resolutions and the development of new computer software for better processing of the data generated by the technique.

Since their introduction in 2006, DECTRIS Hybrid-Pixel-Counting detectors have transformed X-ray research at synchrotrons and in laboratories. Recently, they enabled breakthroughs in Electron Microscopy Materials Science applications such as EELS and 4D-STEM. With this unique development at the LMB, structural biologists will get the chance to accelerate their research using their favorite detector.

References

1. Structure determination by cryoEM at 100 keV. McMullan, G., Naydenova, K., Mihaylov, D., Yamashita, K., Peet, MJ., Wilson, H., Dickerson, JL., Chen, S., Cannone, G., Lee, Y., Hutchings, KA., Gittins, O., Sobhy, MA., Wells, T., El-Gomati, MM., Dalby, J., Meffert, M., Schulze-Briese, C., Henderson, R., Russo, CJ., 2023 PNAS, 120 (49) e2312905120, https://doi.org/10.1073/pnas.2312905120

2. SINGLA product page