Photothermal cantilever actuation for fast single-molecule force spectroscopy

Area of Science:

• Atomic Force Microscopy
• Single-Molecule Biophysics
• Nanotechnology

Background:

• Atomic force microscopy (AFM) is crucial for probing molecular interactions.
• Controlling force precisely is essential for single-molecule force spectroscopy.
• Conventional piezo-based force-clamp systems have limitations in speed and accuracy.

Purpose of the Study:

• To implement and characterize photothermal cantilever excitation for single-molecule force spectroscopy.
• To develop a faster and more accurate force-clamp system for molecular unfolding studies.
• To improve the detection of complete molecular unfolding patterns.

Main Methods:

• Utilized photothermal cantilever excitation via minute heat pulses.
• Combined photothermal actuation with a conventional piezoactuator for force control.
• Implemented simple feedback mechanisms and standard cantilever geometries.

Main Results:

• Achieved step response times of less than 90 microseconds, over an order of magnitude faster than conventional systems.
• Demonstrated high accuracy and large working distances in force-clamp control.
• Successfully unfolded a protein construct (1 green fluorescent protein, 8 immunoglobulin domains) at constant force.

Conclusions:

• Photothermal cantilever excitation provides a fast and easily implementable method for AFM.
• The combined photothermal and piezoactuator system significantly enhances force-clamp spectroscopy performance.
• This technique enables precise and complete analysis of molecular unfolding events.