Photo originally published in Structural Studies of the Giant Mimivirus. PLoS Biol 7(4): e1000092. doi:10.1371/journal.pbio.1000092. License: CC BY 2.5.

By Nathan Levinzon, Neurobiology, Physiology, and Behavior ‘23

Author’s Note: The purpose of this article is to inform the UC Davis community about the arrival and use of a groundbreaking technology to campus. I hope to have provided a comprehensive introduction to Cryo-EM, information on Cryo-EM at UC Davis, and an example of how the technology is already being used to solve problems in biology on campus. I also aim to share my excitement regarding this technology in the hope that I inspire others to pursue this interesting and advancing field of study.

Cryo-electron microscopy, often abbreviated as “Cryo-EM,” is a version of microscopy that uses beams of electrons instead of light to illuminate cryogenically frozen samples. Because the wavelength of an electron is much shorter than the wavelength of light, samples can be imaged at mind-boggling resolutions. After the sample is captured in many orientations, the images are compiled in software to finally resolve a three-dimensional image. “If you want to imagine what it’s like to use this technology,” UC Davis Professor Jawdat Al-Bassam explains in an interview for the College of Biological Sciences, “think about walking into a museum, looking at a statue, taking pictures of it, and figuring out how to put those pictures together to get a three-dimensional picture. In essence, that’s what we do with molecules. They are like small molecular statues, and we take images of them at a variety of angles and orientations. We combine these images to get a design plan for how these molecules are put together ” [1].

As a result of recent advances in technology and software, the progress in the resolution of Cryo-EM seems limitless. New microscopes on the market have brought the lowest resolution down to about two  angstroms—twice the diameter of a hydrogen atom—with even higher resolutions yet to come. Before 2010, scientists could achieve maximum resolutions of about four angstroms. This incredible and exciting variant of microscopy stands to shape the future of biological sciences. Dean of Biological Sciences Mark Winey says that “Cryo-EM is certainly part of the portfolio of technology that any campus like UC Davis should have,” and it’s easy to see why [1]. 

One of the most advanced Cryo-EM microscopes on the market today is the newly released Glacios Cryo-Transmission Electron Microscope (TEM) by Thermo-Fisher. On the surface, the Glacios functions like any other TEM: A cryogenically frozen sample is prepared and shot with electrons that hit a camera in order to resolve a high-resolution, black and white image. What makes this microscope different, however, is its groundbreaking camera. The camera has a pixel size slightly smaller than the area that electrons interact with, which enables a high-speed electron detector to find the center of electron events with sub-pixel precision. The end result is a fourfold increase in resolution from older TEMs while simultaneously reducing aliasing, a sampling error caused by electron interference.

With this microscope, researchers can examine life at the molecular level better than ever before. The closed-system design of the microscope ensures a safe and robust pathway through every step of microscopy, from sample preparation and optimization to image acquisition and data processing of up to twelve samples [2]. Its massive throughput is as impressive as its small footprint, allowing for it to be installed in labs with pre-existing infrastructure. Autonomous sample loading and lense alignment have made Cryo-EM faster and easier for both the budding and seasoned scientist. 

UC Davis has recently made a large investment of its own in Cryo-EM. On January 31, 2020, the College of Biological Sciences celebrated the ribbon-cutting for their own ThermoFisher Scientific Glacios Cryo-Transmission Electron Microscope, outfitted with a Gatan K3 direct detector camera. Festivities were short-lived, however, because labs were already in line to use this new machine. Researchers at Professor Al-Bassam’s lab were some of the first to use this microscope while studying kinesin, a motor protein found in eukaryotic cells. By utilizing Cryo-EM to resolve the structure of kinesin, they concluded that kinesin’s tails open a part of the motor that encapsulates ATP, slowing the movement of these motors and allowing kinesin to cluster and work together. With this new microscope in hand, these researchers are now able to unravel the functions of kinesin and how it interacts with other kinesin to move and group. The complete paper discussing the binding between kinesin tail and motor domains and its function in microtubule sliding can be found in the January 2020 edition of eLife [3]. 

Cryo-EM has never been easier, safer, and more accessible to use UC Davis. With the purchase of the Glacios, UC Davis has made itself ready to introduce a new generation of researchers to the field of modern biology. Resolutions that were thought impossible ten years ago are now a reality, and new advancements continue to push the bounds at which samples can be imaged at. With the quickening pace of advancements in Cryo-EM, there is no telling what mysteries researchers at UC Davis will uncover next.

References

1. Slipher, David, et al. “CRYO EM: Unleashing the Future of Biology at UC Davis.” UC Davis College of Biological Sciences, 31 Jan. 2020, biology.ucdavis.edu/cryo-em. Accessed 23 Mar. 2020.
2. “Cryo TEM: Cryo-EM.” Thermo Fisher Scientific – US, www.thermofisher.com/us/en/home/electron-microscopy/products/transmission-electron-microscopes/glacios-cryo-tem.html.
3. Bodrug, Tatyana, et al. “The Kinesin-5 Tail Domain Directly Modulates the Mechanochemical Cycle of the Motor Domain for Anti-Parallel Microtubule Sliding.” ELife, vol. 9, 2020, doi:10.7554/elife.51131.