A force calibration standard for magnetic tweezers

Area of Science:

• Biophysics
• Molecular Biology
• Biochemistry

Background:

• Single-molecule force spectroscopy is crucial for studying biological macromolecules and enzymatic reactions under force.
• Magnetic tweezers (MTs) are powerful tools due to their simplicity, non-invasive nature, high throughput, and broad force range.
• Accurate force determination in MTs is challenging for short biomolecules at high forces and long tethers at low forces (<1 pN).

Purpose of the Study:

• To develop a reliable calibration standard for magnetic tweezers to overcome limitations in accurate force determination.
• To provide generalized force calibrations applicable to commonly used magnetic microspheres.
• To enhance the precision and reduce variability in magnetic tweezers experiments.

Main Methods:

• Developed a calibration standard using four magnet configurations and two types of commercially available magnetic microspheres.
• Calculated forces in both time and spectral domains by analyzing bead fluctuations.
• Validated calibration curves using different algorithms, demonstrating close agreement.

Main Results:

• Generated calibration curves spanning forces from 100 piconewtons down to tens of femtonewtons.
• Demonstrated accurate force determination across a broad force range, addressing limitations of previous methods.
• Achieved close agreement between different algorithms, confirming the robustness of the calibration.

Conclusions:

• The presented calibration standard offers a convenient resource for magnetic tweezers users.
• This work diminishes experimental variations between different configurations and laboratories.
• Improved force calibration enhances the reliability and reproducibility of single-molecule biophysics experiments.