Mechanical unfolding of alpha2-macroglobulin molecules with atomic force microscope

Area of Science:

• Biophysics
• Materials Science
• Biochemistry

Background:

• Atomic Force Microscopy (AFM) is a powerful tool for probing molecular interactions and mechanical properties.
• Understanding protein mechanics is crucial for deciphering biological functions and developing novel biomaterials.

Purpose of the Study:

• To investigate the mechanical stretching and unfolding behavior of alpha2-macroglobulin (A2M) at the single-molecule level.
• To utilize AFM force spectroscopy to analyze protein-substrate interactions.

Main Methods:

• Derivatization of alpha2-macroglobulin using a sulfhydryl cross-linker.
• Attachment of derivatized A2M between gold-coated mica substrate and silicon nitride AFM tip.
• Performing atomic force microscopy force curve measurements to analyze cantilever deflection during retraction.

Main Results:

• An extensive downward cantilever deflection was observed exclusively when the substrate was coated with derivatized alpha2-macroglobulin.
• This deflection indicates a significant force applied to the cantilever during the retraction phase.
• The observed phenomenon was attributed to the mechanical stretching and subsequent unfolding of single or few A2M molecules.

Conclusions:

• Single alpha2-macroglobulin molecules exhibit mechanical unfolding under AFM analysis.
• The derivatization and AFM force spectroscopy method effectively probes protein mechanical properties.
• This study provides insights into the mechanical behavior of A2M, relevant for biophysical and materials science applications.