Correction-free force calibration for magnetic tweezers experiments

E. Ostrofet, F.S. Papini, D. Dulin

Research output: Contribution to JournalArticleAcademicpeer-review


© 2018, The Author(s).Magnetic tweezers are a powerful technique to perform high-throughput and high-resolution force spectroscopy experiments at the 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. However, magnetic tweezers experiments require an accurate force calibration to extract quantitative data, which is limited to low forces if the deleterious effect of the finite camera open shutter time (τsh) is not corrected. Here, we provide a simple method to perform correction-free force calibration for high-throughput magnetic tweezers at low image acquisition frequency (fac). By significantly reducing τsh to at least 4-fold the characteristic times of the tethered magnetic bead, we accurately evaluated the variance of the magnetic bead position along the axis parallel to the magnetic field, estimating the force with a relative error of ~10% (standard deviation), being only limited by the bead-to-bead difference. We calibrated several magnets - magnetic beads configurations, covering a force range from ~50 fN to ~60 pN. In addition, for the presented configurations, we provide a table with the mathematical expressions that describe the force as a function of the magnets position.
Original languageEnglish
Article number15920
JournalScientific Reports
Issue number1
Publication statusPublished - 1 Dec 2018
Externally publishedYes


D.D. was supported by the Interdisciplinary Center for Clinical Research (IZKF) at the University Hospital of the University of Erlangen-Nuremberg. We would like to thank Jelmer Cnossen for assistance in software installation, Alexander Steinkasserer and the Optical Imaging Center Erlangen (OICE) for granting us access to their molecular biology lab. We would also like to thank Francesco Pedaci, Yera Ussembayev, Mona Seifert and Monika Spermann for reading the manuscript.

FundersFunder number
Interdisciplinary Center for Clinical Research
University of Erlangen-Nuremberg


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