Advances in Single-Particle Electron Cryomicroscopy Structure Determination applied to Sub-tomogram Averaging

Area of Science:

• Structural Biology
• Microscopy Techniques
• Biophysics

Background:

• Single-particle electron cryomicroscopy (cryo-EM) has advanced significantly.
• Electron cryotomography (cryo-ET) and sub-tomogram averaging offer powerful tools for structural determination.
• Radiation-induced specimen movement is a known challenge in cryo-EM and cryo-ET.

Purpose of the Study:

• To adapt recent cryo-EM innovations for improved cryo-ET and sub-tomogram averaging.
• To investigate and mitigate radiation-induced specimen movement during tomographic data acquisition.
• To achieve higher resolution structures of biological macromolecules using cryo-ET.

Main Methods:

• Implementation of a novel 3D contrast transfer function model within RELION.
• Application of single-particle analysis and sub-tomogram averaging to direct electron detector data.
• Utilizing ultrastable gold substrates to reduce specimen movement.

Main Results:

• Significant radiation-induced specimen movements were observed during cryo-ET data collection.
• Ultrastable gold substrates substantially reduced these movements.
• A sub-nanometer resolution structure of the hepatitis B capsid was obtained.

Conclusions:

• Reducing radiation-induced specimen movement is crucial for enhancing cryo-ET resolution.
• The implemented methods show promise for improving tomogram quality and structural detail.
• Further advancements in minimizing specimen movement will be key for future cryo-ET studies.