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Magnetic Tweezers for the Measurement of Twist and Torque
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Optical Torque Calculations and Measurements for DNA Torsional Studies.

Yifeng Hong, Fan Ye, Jin Qian

    Biorxiv : the Preprint Server for Biology
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    PubMed
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    This study introduces a new simulation platform and experimental method to accurately measure DNA torsional properties using angular optical traps (AOTs). The findings validate the simulation

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    Area of Science:

    • Biophysics
    • Optical Tweezers
    • Molecular Mechanics

    Background:

    • Angular optical traps (AOTs) are crucial for studying biological molecule mechanics.
    • Spherical aberrations in AOTs, caused by the objective lens, complicate torque measurements.
    • Experimental understanding of these aberrations' impact on DNA torsional mechanics is limited.

    Purpose of the Study:

    • To develop a theoretical and experimental framework for accurate force and torque measurements in AOTs, accounting for spherical aberrations.
    • To investigate the impact of spherical aberrations on DNA torsional mechanics measurements.
    • To validate a new simulation platform and experimental methodology.

    Main Methods:

    • Developed a finite element method (FEM) based numerical platform to calculate forces and torques on trapped particles.
    • Implemented a novel experimental method using DNA as a molecular ruler to measure focal shifts caused by spherical aberrations.
    • Compared simulation predictions with experimental measurements of focal shift, trap stiffness, and DNA torsional properties.

    Main Results:

    • Calculated and measured focal shift ratios due to spherical aberrations showed good agreement.
    • Angular trap stiffness was accurately predicted and experimentally verified across different trap heights and displacements.
    • Intrinsic DNA torsional properties were robustly determined, confirming the validity of the developed methodology.

    Conclusions:

    • The developed FEM simulation platform accurately predicts forces and torques in AOTs, considering spherical aberrations and particle properties.
    • Experimental validation confirmed the simulation's accuracy, enabling robust measurement of DNA torsional mechanics.
    • This framework facilitates improved particle design and measurement accuracy for single-molecule assays using AOTs.