Regensburg 2013 – scientific programme

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BP: Fachverband Biologische Physik

BP 8: Posters: Proteins

BP 8.17: Poster

Monday, March 11, 2013, 17:30–19:30, Poster B2

Video-based and interference-free axial force detection and analysis for optical tweezers — •Sebastian Knust, Andre Spiering, Andy Sischka, and Dario Anselmetti — Experimental Biophysics & Applied Nanoscience, Faculty of Physics, Bielefeld University, 33615 Bielefeld, Germany

For measuring the minute forces exerted on single molecules during controlled translocation through nanopores with sub-piconewton precision, we have developed a video-based axial force detection and analysis system for optical tweezers [1].

As the bandwidth of the system is not as high as in backscattered light based systems, we integrated Allan variance analysis [2] for trap stiffness calibration.

Upon manipulating a microbead in the vicinity of a weakly reflecting surface with simultaneous axial force detection, interference effects have to be considered [3]. We measured and analyzed the backscattering light properties of polystyrene and silica microbeads with different diameters and propose distinct and optimized experimental configurations (microbead material and diameter) for minimal light backscattering and virtually interference-free microbead position detection.

As a proof of principle, we investigated the nanopore threading forces of a single dsDNA strand attached to a microbead with an overall force resolution of ±0.5 pN at a sample rate of 123 Hz.

[1] S. Knust et. al., Rev. Sci. Instrum. 83, 103704 (2012)

[2] B. Lansdorp, O. Saleh, Rev. Sci. Instrum. 83, 025115 (2012)

[3] A. Sischka et. al., Rev. Sci. Instrum. 79, 63702 (2008)