A Medipix quantum area detector allows rotation electron diffraction data collection from submicrometre...

Area of Science:

• Crystallography
• Materials Science
• Biophysics

Background:

• X-ray radiation damage limits diffraction data collection from submicrometre protein crystals.
• Conventional rotation data collection is impossible for 100 nm crystals, even with advanced techniques.

Purpose of the Study:

• To demonstrate the feasibility of collecting rotation electron diffraction data from single, small protein crystals.
• To adapt X-ray crystallography methods for analyzing electron diffraction data from nanocrystals.

Main Methods:

• Utilized a Medipix2 quantum area detector with high sensitivity at a very low electron dose (≤ 0.1 e⁻ Å⁻²).
• Collected a 30-frame rotation series of 200 keV electron diffraction data from a single ~100 nm protein crystal.
• Employed a highly parallel 200 keV electron beam (λ = 0.025 Å).

Main Results:

• Achieved successful data collection from a single nanocrystal, overcoming previous limitations.
• Observed Ewald sphere curvature at low resolution, indicating a low mosaic spread/beam divergence (≤ 0.4°).
• Demonstrated that X-ray crystallography software (MOSFLM, SCALA) can be applied to analyze electron diffraction data.

Conclusions:

• Electron diffraction at low doses is viable for collecting rotation data from single protein nanocrystals.
• This technique allows pinpointing crystal volumes with low mosaicity.
• Established a foundation for applying established X-ray crystallography data analysis strategies to electron diffraction data from protein nanocrystals.