Prospects for using an IVEM with a FEG for imaging macromolecules towards atomic resolution

Area of Science:

• Electron microscopy
• Structural biology
• Materials science

Background:

• Advancements in specimen preparation and imaging techniques are crucial for high-resolution biological macromolecule analysis.
• Field emission guns (FEGs) offer superior spatial and temporal coherence for electron microscopy, enabling near-atomic resolution imaging.

Purpose of the Study:

• To evaluate the potential of field emission gun technology in intermediate-voltage electron microscopes (IVEMs) for high-resolution imaging of biological macromolecules.
• To determine optimal imaging conditions for achieving atomic resolution in biological samples.

Main Methods:

• Computational analysis of carbon film images acquired using a 200 kV Hitachi microscope with a cold field emission gun.
• Varying defocus conditions (Scherzer focus to 1.1 microns underfocus) to assess contrast and resolution.
• Theoretical considerations for intermediate-voltage electron microscopy (IVEM) in biological imaging.

Main Results:

• Detectable contrast beyond 3.5 Angstrom resolution was observed in carbon film images.
• Large defocus, commonly used for low-resolution contrast in biological imaging, can be optimized.
• Intermediate-voltage electron microscopy (IVEM) theoretically offers improved contrast at high resolution by minimizing temporal coherent effects.

Conclusions:

• Field emission gun technology is essential for achieving near-atomic resolution in biological macromolecule imaging.
• Intermediate-voltage electron microscopes (IVEMs) equipped with FEGs are promising for reliable interpretation and reconstruction of large biological assemblies.
• Further development of IVEMs with FEGs is warranted for advancing biological macromolecule imaging towards atomic resolution.