Pursuing the physics of cryo-EM image formation

Area of Science:

• Structural Biology
• Biophysics
• Microscopy

Background:

• Cryo-electron microscopy (cryo-EM) enables near-atomic resolution imaging of biological molecules.
• Current reconstruction algorithms rely on simplified projection and weak-phase approximations.
• The physics of electron imaging is more complex and potentially under-exploited.

Purpose of the Study:

• Revisit fundamental principles of image formation in cryo-EM.
• Derive the contrast transfer function (CTF) from first principles.
• Introduce a new reconstruction algorithm, Ghostbuster, using a physically accurate forward model.

Main Methods:

• First-principles derivation of image formation physics in cryo-EM.
• Analysis of electron-matter interaction, wave propagation, and image detection.
• Development and application of the Ghostbuster reconstruction algorithm.

Main Results:

• Demonstrated how the conventional CTF model arises from underlying physics.
• Introduced Ghostbuster, a novel algorithm leveraging a physically accurate forward model.
• Provided a physically grounded approach to assess cryo-EM assumptions.

Conclusions:

• Understanding the full physics of electron imaging can enhance cryo-EM capabilities.
• Ghostbuster offers a path beyond conventional CTF-based reconstruction.
• This work provides context for future methodological developments in cryo-EM.