Correction-free force calibration for magnetic tweezers experiments

Area of Science:

• Biophysics
• Single-molecule biophysics
• Nanotechnology

Background:

• Magnetic tweezers are essential for high-throughput, high-resolution single-molecule force spectroscopy.
• Accurate force calibration is critical for quantitative data extraction in magnetic tweezers experiments.
• The finite camera shutter time (τsh) limits force calibration accuracy at low forces.

Purpose of the Study:

• To develop a simple, correction-free method for accurate force calibration in high-throughput magnetic tweezers.
• To address the limitations imposed by camera shutter time on force measurement accuracy.
• To enable reliable quantitative analysis of mechanochemical behaviors of biomolecules.

Main Methods:

• Implementing a method to reduce camera open shutter time (τsh) significantly.
• Utilizing low image acquisition frequency (fac) for enhanced calibration.
• Measuring the variance of magnetic bead position along the magnetic field axis.
• Calibrating multiple magnet-bead configurations across a wide force range (50 fN to 60 pN).

Main Results:

• Achieved correction-free force calibration for high-throughput magnetic tweezers.
• Reduced τsh to at least 4-fold the characteristic times of the tethered magnetic bead.
• Estimated force with a relative error of ~10% (standard deviation), limited by bead-to-bead variation.
• Provided a table of mathematical expressions for force calculation based on magnet position.

Conclusions:

• The developed method offers accurate and efficient force calibration for magnetic tweezers.
• This technique enhances the reliability of quantitative data from single-molecule force spectroscopy.
• The findings support high-throughput characterization of nucleic acids and enzymes' mechanochemical properties.