Sub-angstrom conformational changes of a single molecule captured by AFM variance analysis

Area of Science:

• Biophysics
• Polymer Physics
• Single-Molecule Biophysics

Background:

• Thermodynamic equilibrium is crucial for understanding molecular dynamics.
• Variance analysis offers a high-resolution method to probe system dynamics.
• Single-molecule techniques provide insights into molecular behavior under force.

Purpose of the Study:

• To utilize equilibrium variance analysis for probing dextran molecule dynamics.
• To establish thermodynamic equilibrium and detect unobservable conformational changes in dextran.
• To validate a novel variance analysis method for molecular studies.

Main Methods:

• Single-molecule atomic-force microscopy (AFM) was employed.
• Variance analysis of single dextran molecule length fluctuations was performed.
• Force-extension curves were analyzed to verify thermodynamic equilibrium.

Main Results:

• Equilibrium variance analysis confirmed thermodynamic equilibrium throughout the force-extension curve.
• The variance analysis detected a sub-Angstrom intermediate conformation during the chair-to-boat transition.
• Conformational changes were identified that are not observable by other methods.

Conclusions:

• Equilibrium variance analysis is a powerful tool for high-resolution molecular dynamics studies.
• This method successfully identified a previously undetected intermediate conformation in dextran.
• The approach is broadly applicable to various molecules, including proteins, for thermal equilibrium testing and variance analysis.