A spotlight on MicroED at CEMAS

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Figure A) Diffraction pattern of a carbamazepine crystal. Figure B) Top: carbamazepine modeled into density; bottom: carbamazepine molecule as a skeletal formula.
Figure A) Diffraction pattern of a carbamazepine crystal. Figure B) Top: carbamazepine modeled into density; bottom: carbamazepine molecule as a skeletal formula.

Micro-Electron Diffraction (MicroEd) has created excitement in the scientific community as a new electron microscopy method to determine the structure of nano-sized crystals. These nanocrystals are too small for traditional X-ray crystallography. 

Ohio State’s Center for Electron Microscopy and Analysis (CEMAS) is positioned to amplify characterization capabilities and advance research involving MicroED. The MicroED system is currently installed on CEMAS’ Thermo Scientific Glacios Cryo-TEM. 

In this method, the crystal is continuously tilted in the cryo-electron microscope (cryo-EM) while diffraction information is recorded. The use of nano-sized crystals overcomes a significant bottleneck in X-ray crystallography, which requires micron-sized crystals or larger. Furthermore, MicroED data exploits already existing analysis programs that were originally written for X-ray diffraction.

Nicole Hoefer, a post-doctoral scholar at CEMAS, recently hosted a virtual edition of our Beyond the Scope: CEMAS Discussion Series dedicated to MicroED. She is trained in MicroED techniques and has kickstarted data collection to validate the system at CEMAS. During the presentation, she shares additional insight into MicroED, reviews the experiential workflow, and details some recently determined structures. View the recording

MicroED has produced several protein and small-molecule structures (1-3). At CEMAS, we’re excited about the potential and looking forward to amplifying characterization capabilities. Over the last several months, the MicroED program at CEMAS has experienced several headlining milestones: 

1. CEMAS establishes MicroED workflow

The team at CEMAS has developed an established workflow for the acquisition and analysis of electron diffraction data consisting of sample preparation, collection of diffraction data, and data analysis. Team members were trained to analyze electron diffraction data through a workshop offered by the Gonen Laboratory at the University of California, Los Angeles. Before the transition to remote work during the COVID-19 pandemic, the CEMAS team successfully centralized its analysis software on a remotely accessible Linux virtual machine. This achievement has been critical to foster continued advancement remotely. 

2. CEMAS validates MicroED system

CEMAS team members chose to validate their system using two small molecules: carbamazepine and biotin. The data produced compare well with previously published results (Figure 1, [3]). The team’s focus has transitioned to obtaining quality diffraction data for standard proteins, like lysozyme. 

3. Identification of promising projects

The CEMAS team is actively seeing insight from the Ohio State research community and beyond for potential projects. Even if you’re not sure if MicroED is the right fit, we welcome your inquiry to explore opportunities further. Please connect with Nicole Hoefer at hoefer.3@osu.edu if you’re interested in collaborating. 

 

 

References:

  1. Shi, Dan; Nannenga, Brent; Iadanza, Matthew; Gonen, Tamir; Three-dimensional electron crystallography of protein microcrystals; Elife, 2 , pp. e01345, 2013.
  2. Jones, Christopher; Martynowycz, Michael; Hattne, Johan; Fulton, Tyler; Stoltz, Brian; Rodriguez, Jose; Nelson, Hosea; Gonen, Tamir; The CryoEM Method MicroED as a Powerful Tool for Small Molecule Structure Determination; ACS Cent Sci, 4 (11), pp. 1587–1592, 2018.
  3. Nannenga, Brent; Gonen, Tamir; The cryo-EM method microcrystal electron diffraction (MicroED); Nat. Methods, 16 (5), pp. 369–379, 2019.