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BP: Fachverband Biologische Physik

BP 19: Poster VII

BP 19.23: Poster

Dienstag, 17. März 2020, 14:00–16:00, P2/3OG

In situ magnetic tweezers force calibration for all tether length — •Eugeniu Ostrofet, Flavia Stal-Papini, and David Dulin — FAU, Erlangen, Germany

Magnetic tweezers are a powerful technique to perform high-throughput and high-resolution force spectroscopy measurements at single-molecule level. The camera-based detection of magnetic tweezers enables the observation of hundreds of magnetic beads in parallel, and therefore the characterization of the mechanochemical behavior of hundreds of nucleic acids and enzymes. The accuracy of force spectroscopy measurements relies on a precise force calibration. In magnetic tweezers, the forces are quantified from the lateral fluctuations of the tethered magnetic bead. Such measurements are difficult to perform on short tethers, i.e. less than 4 kbp DNA, and therefore often rely on calibration tables, i.e. magnetic force versus magnets distance, performed using long DNA molecules, i.e. ~8 kbp and longer. However, the bead-to-bead variation in magnetic content leads to force dispersion, which biases the force spectroscopy measurement. To solve this issue, we present a new and simple strategy to perform in situ force calibration for hundreds of tethered magnetic beads simultaneously, for any tether length, and for the whole accessible force range for a given magnets-magnetic bead configuration. We illustrate the usefulness of our approach by characterizing the force dependence of protein-DNA interactions using a DNA hairpin-based force jump assay.