Conical Fourier shell correlation applied to electron tomograms.

Area of Science:

• Structural biology
• Microscopy techniques
• Image processing

Background:

• Electron tomogram resolution is limited by anisotropic effects from data collection geometry.
• Dual-axis tilt series acquisition can mitigate these anisotropic resolution issues.

Purpose of the Study:

• To evaluate the benefit of dose fractionation for dual-axis cryo-electron tomography.
• To compare the resolution isotropy of single-axis versus dual-axis electron tomograms.
• To introduce a novel metric, conical Fourier shell correlation (cFSCe/o), for assessing tomographic reconstruction quality.

Main Methods:

• Development and application of conical Fourier shell correlation (cFSCe/o) for resolution isotropy assessment.
• Comparison of single-axis and dual-axis (cryo-)electron tomograms using even/odd data splits.
• Evaluation of different alignment methods for dual-axis tomograms.

Main Results:

• Dual-axis tomograms exhibit improved resolution isotropy in the plane orthogonal to the electron beam compared to single-axis.
• High-resolution artifacts along the tilt axis are reduced in dual-axis acquisitions.
• Different reconstruction programs yield varying degrees of anisotropy in dual-axis tomograms.

Conclusions:

• Dual-axis electron tomography offers enhanced resolution isotropy, particularly when dose is fractionated.
• cFSCe/o is a valuable tool for comparing acquisition parameters, reconstruction methods, and hardware in electron tomography.
• Optimizing dual-axis acquisition and reconstruction is crucial for achieving isotropic resolution in cryo-electron tomography.