Modular microfluidics enables kinetic insight from time-resolved cryo-EM.

Area of Science:

• Biochemistry and Structural Biology
• Biophysical Chemistry
• Cryo-Electron Microscopy

Background:

• Understanding biochemical reaction mechanisms requires both structural and kinetic data.
• Existing methods often struggle to capture dynamic intermediates, relying on static structures or potentially artefactual stabilization techniques.
• A need exists for methods that can capture transient states without altering reaction pathways.

Purpose of the Study:

• To develop and validate a novel time-resolved sample preparation method for cryo-electron microscopy (trEM).
• To enable the visualization of short-lived reaction intermediates with high structural resolution.
• To overcome limitations of current techniques in studying dynamic biochemical processes.

Main Methods:

• Development of a modular microfluidic device for automated, fast, and blot-free sample vitrification.
• Incorporation of a 3D-mixing unit and variable delay lines for precise temporal control.
• Application of trEM for capturing structural snapshots of biochemical reactions at sub-second timescales.

Main Results:

• The trEM method successfully preserves high-resolution structural detail of macromolecules.
• Demonstrated improved sample integrity and protein distribution within vitreous ice.
• Visualized reaction intermediates of early RecA filament growth across three orders of magnitude on sub-second timescales.

Conclusions:

• The reported trEM method provides a versatile, reproducible, and automated approach for studying dynamic biological processes.
• This technique significantly enhances the ability to investigate reaction mechanisms at the molecular level.
• trEM is readily adaptable to a broad spectrum of fundamental biological questions requiring time-resolved structural information.