TweezPal – Optical tweezers analysis and calibration software

Optical tweezers, a powerful tool for optical trapping, micromanipulation and force transduction, have in recent years become a standard technique commonly used in many research laboratories and university courses. Knowledge about the optical force acting on a trapped object can be gained only after a calibration procedure which has to be performed (by an expert) for each type of trapped objects. In this paper we present TweezPal, a user-friendly, standalone Windows software tool for optical tweezers analysis and calibration. Using TweezPal, the procedure can be performed in a matter of minutes even by non-expert users. The calibration is based on the Brownian motion of a particle trapped in a stationary optical trap, which is being monitored using video or photodiode detection. The particle trajectory is imported into the software which instantly calculates position histogram, trapping potential, stiffness and anisotropy.Program summaryProgram title: TweezPalCatalogue identifier: AEGR_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGR_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 44 891No. of bytes in distributed program, including test data, etc.: 792 653Distribution format: tar.gzProgramming language: Borland DelphiComputer: Any PC running Microsoft WindowsOperating system: Windows 95, 98, 2000, XP, Vista, 7RAM: 12 MbytesClassification: 3, 4.14, 18, 23Nature of problem: Quick, robust and user-friendly calibration and analysis of optical tweezers. The optical trap is calibrated from the trajectory of a trapped particle undergoing Brownian motion in a stationary optical trap (input data) using two methods.Solution method:   Elimination of the experimental drift in position data. Direct calculation of the trap stiffness from the positional variance. Calculation of 1D optical trapping potential from the positional distribution of data points. Trap stiffness calculation by fitting a parabola to the trapping potential. Presentation of X–YX–Y positional density for close inspection of the 2D trapping potential. Calculation of the trap anisotropy.Running time: Seconds