Optical torque calculations and measurements for DNA torsional studies.

Autor:	Hong Y; Department of Electrical and Computer Engineering, Cornell University, Ithaca, New York., Ye F; Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York., Qian J; Department of Physics & LASSP, Cornell University, Ithaca, New York., Gao X; Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York., Inman JT; Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York., Wang MD; Howard Hughes Medical Institute, Cornell University, Ithaca, New York; Department of Physics & LASSP, Cornell University, Ithaca, New York. Electronic address: mwang@physics.cornell.edu.
Jazyk:	angličtina
Zdroj:	Biophysical journal [Biophys J] 2024 Sep 17; Vol. 123 (18), pp. 3080-3089. Date of Electronic Publication: 2024 Jul 03.
DOI:	10.1016/j.bpj.2024.07.005
Abstrakt:	The angular optical trap (AOT) is a powerful instrument for measuring the torsional and rotational properties of a biological molecule. Thus far, AOT studies of DNA torsional mechanics have been carried out using a high numerical aperture oil-immersion objective, which permits strong trapping but inevitably introduces spherical aberrations due to the glass-aqueous interface. However, the impact of these aberrations on torque measurements is not fully understood experimentally, partly due to a lack of theoretical guidance. Here, we present a numerical platform based on the finite element method to calculate forces and torques on a trapped quartz cylinder. We have also developed a new experimental method to accurately determine the shift in the trapping position due to the spherical aberrations by using a DNA molecule as a distance ruler. We found that the calculated and measured focal shift ratios are in good agreement. We further determined how the angular trap stiffness depends on the trap height and the cylinder displacement from the trap center and found full agreement between predictions and measurements. As a further verification of the methodology, we showed that DNA torsional properties, which are intrinsic to DNA, could be determined robustly under different trap heights and cylinder displacements. Thus, this work has laid both a theoretical and experimental framework that can be readily extended to investigate the trapping forces and torques exerted on particles with arbitrary shapes and optical properties. Competing Interests: Declaration of interests The authors declare no competing interests. (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)
Databáze:	MEDLINE
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