Stepwise unfolding of titin under force-clamp atomic force microscopy

Area of Science:

• Biophysics
• Molecular Biology
• Biotechnology

Background:

• Proteins like titin are crucial for muscle elasticity and cellular functions.
• Understanding protein mechanical stability is key to deciphering biological processes.
• Existing methods have limitations in directly probing force-dependent unfolding.

Purpose of the Study:

• To implement and validate a single-molecule force clamp technique.
• To investigate the mechanical unfolding of engineered titin protein modules.
• To directly measure the force dependence of protein unfolding probabilities.

Main Methods:

• Adaptation of an atomic force microscope (AFM) for single-molecule force clamp measurements.
• Engineering of titin protein constructs for controlled unfolding studies.
• Analysis of protein elongation steps and waiting times for unfolding events.

Main Results:

• Demonstrated stepwise elongation of engineered titin protein modules under force clamp.
• Observed exponentially distributed waiting times for module unfolding.
• Quantified differences in mechanical stability between I27 and I28 titin modules.

Conclusions:

• Single-molecule force clamp spectroscopy is a powerful tool for probing protein mechanics.
• The method directly measures force-dependent unfolding probabilities.
• This technique offers a direct approach to study the mechanical stability of elastic proteins relevant to muscle, extracellular matrix, and cell adhesion.