Probing the mechanical stability of proteins using the atomic force microscope.

Area of Science:

• Biophysics
• Molecular Biology
• Materials Science

Background:

• The mechanical properties of single protein molecules are crucial for understanding their function and stability.
• Atomic force microscopy (AFM) is a powerful tool for probing these properties at the single-molecule level.

Purpose of the Study:

• To investigate the mechanical strength of single protein molecules using AFM.
• To identify key factors determining protein mechanical strength, such as secondary structure and force application.
• To explore the influence of ligand binding and unfolding pathways on protein mechanical resistance.

Main Methods:

• Single-molecule force spectroscopy using atomic force microscopy (AFM).
• Mechanical unfolding of various protein types under controlled force application.
• Analysis of force-extension curves to determine mechanical strength and stability.

Main Results:

• Protein mechanical strength is significantly influenced by the type of secondary structure and its orientation relative to the points of force application.
• Unlike chemical denaturants, mechanical force acts locally, allowing for tunable apparent mechanical weakness or strength based on the unfolding pathway.
• Ligand binding can modulate a protein's mechanical resistance depending on the relative locations of the binding site and the applied force.

Conclusions:

• The mechanical strength of proteins is highly sensitive to the applied force and the protein's structural features.
• Mechanical deformation can play a role in the in vivo degradation or remodeling of proteins and their complexes.
• AFM provides unique insights into the local and context-dependent mechanical behavior of proteins.