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15 October 2015 Calibration of a dual-trap optical tweezers for single molecule force spectroscopy study
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Optical tweezers has shown its significant advantages in applying pico-Newton force on micro beads and handling them with nanometer-level precision, and becomes a powerful tool for single-molecule biology. Many excellent researching results in use of the optical tweezers have been reported. Most of them focus on the single-trap optical tweezers experiments. However, when a single-trap optical tweezers is applied to biological molecule, there is often an obvious noise from the sample chamber holder to which one end of the sample molecule is tethered. In contrast, a dual-trap optical tweezers can intrinsically avoid this problem because both ends of the sample tethered to microspheres are manipulated with two separate optical traps. In order to force the molecule precisely, it is of importance to do calibrations for both traps. Many approaches have been studied to obtain the stiffness and sensitivity of the trap, but those are not quite suitable for making calibration during experiment. Here, we use a modified method of power spectrum density (PSD) for the calibrations of the stiffness and sensitivity of the traps, which combines a sinusoidal motion of the sample stage. The main strength of the method is that the beads used for the calibration also can be used in experiment later. In addition, the calibration can be performed during experiment. Finally, an experiment using a dsDNA molecule to test the system is presented. The results show that the calibration approach for the dual-trap optical tweezers is efficient and accurate.
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Guoqing Wang, Chunguang Hu, Xiaoqing Gao, Chenguang Su, Sirong Wang, Hai Lei, Xiaodong Hu, Hongbin Li, and Xiaotang Hu "Calibration of a dual-trap optical tweezers for single molecule force spectroscopy study", Proc. SPIE 9672, AOPC 2015: Advanced Display Technology; and Micro/Nano Optical Imaging Technologies and Applications, 96720P (15 October 2015);

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