Effect of compressive force on unbinding specific protein-ligand complexes with force spectroscopy

Area of Science:

• Biophysics
• Biochemistry
• Molecular Interactions

Background:

• Atomic force microscopy (AFM) is a key technique for studying molecular interactions.
• AFM typically analyzes complex formation, rupture forces, and force-distance curves to understand molecular behavior.
• Interpreting AFM data requires careful consideration of experimental parameters.

Purpose of the Study:

• To investigate the impact of contact force on the unbinding profiles of specific and non-specific molecular interactions using AFM.
• To determine if minimizing contact force enhances the specificity of AFM-based molecular interaction studies.

Main Methods:

• Utilized AFM to measure unbinding forces and binding probabilities.
• Examined the lactose-galectin-3 (G3) system as a cognate ligand-receptor pair.
• Used control pairs (mannose-G3 and lactose-KDPG aldolase) with negligible solution-phase affinity.

Main Results:

• Increased contact forces (>250 pN) enhanced binding probabilities and reduced blocking efficiencies for lactose-G3.
• Higher contact forces induced non-specific ruptures in control systems, mimicking specific interactions.
• Non-specific ruptures in control pairs were indistinguishable from specific lactose-G3 interactions at elevated contact forces.

Conclusions:

• Experimental design, particularly contact force, is critical for obtaining interpretable AFM data.
• Minimizing contact force in AFM experiments is essential for selectively probing specific ligand-receptor interactions.
• This approach improves the accuracy of measuring unbinding forces and rupture lengths in molecular recognition studies.