Unbinding molecular recognition force maps of localized single receptor molecules by atomic force microscopy

Area of Science:

• Biophysics
• Surface Science
• Molecular Interactions

Background:

• Atomic force microscopy (AFM) enables single-molecule analysis of biological processes.
• Previous studies lacked detailed adhesion force mapping at the molecular level.

Purpose of the Study:

• To apply AFM's jumping mode for high-resolution mapping of avidin-biotin unbinding forces.
• To analyze the rupture force distribution of single avidin-biotin interactions.
• To investigate the impact of polymer spacer dynamics on force measurements.

Main Methods:

• Utilized AFM in force-scan based jumping mode to acquire simultaneous topographic and adhesion maps.
• Applied the technique to the well-defined avidin-biotin molecular system.
• Collected data at a scanning rate of 250 pixels/s, limited by hydrodynamic drag.

Main Results:

• Achieved laterally resolved adhesion maps of avidin-biotin unbinding forces, correlating with topographic features of single avidin molecules.
• Constructed a rupture-force distribution histogram representative of single molecular interactions.
• Observed that polymer spacer motility leads to deviations from normal force application, introducing measurement errors.

Conclusions:

• AFM's jumping mode provides precise, spatially resolved measurements of single-molecule unbinding forces.
• The avidin-biotin system's rupture forces can be accurately characterized using this method.
• Polymer spacer dynamics are a critical factor to consider for accurate single-molecule force spectroscopy.