Identification and correction of miscalibration artifacts based on force noise for optical tweezers experiments

Single-molecule force spectroscopy using optical tweezers continues to provide detailed insights into the behavior of nanoscale systems. Obtaining precise measurements of their mechanical properties is highly dependent on accurate instrument calibration. Therefore, instrumental drift or inaccurate calibration may prevent reaching an accuracy at the theoretical limit and may lead to incorrect conclusions. Commonly encountered sources of error include inaccuracies in the detector sensitivity and trap stiffness and neglecting the non-harmonicity of an optical trap at higher forces. Here, we first quantify the impact of these artifacts on force-extension data and find that a small deviation of the calibration parameters can already have a significant downstream effect. We then develop a method to identify and remove said artifacts based on differences in the theoretical and measured noise of bead fluctuations. By applying our procedure to both simulated and experimental data, we can show how effects due to miscalibration and trap non-linearities can be successfully removed. Most importantly, this correction can be performed post-measurement and could be adapted for data acquired using any force spectroscopy technique. (c) 2021 Author(s).