Quantifying Force and Viscoelasticity Inside Living Cells Using an Active–Passive Calibrated Optical Trap

Christine M. Ritter, Josep Maes, Lene Oddershede, Kirstine Berg-Sørensen

Research output: Chapter in Book/Report/Conference proceedingBook chapterResearchpeer-review

Abstract

As described in the previous chapters, optical tweezers have become a tool of precision for in vitro single-molecule investigations, where the single molecule of interest most often is studied in purified form in an experimental assay with a well-controlled fluidic environment. A well-controlled fluidic environment implies that the physical properties of the liquid, most notably the viscosity, are known and the fluidic environment can, for calibrational purposes, be treated as a simple liquid.
In vivo, however, optical tweezers have primarily been used as a tool of manipulation and not so often for precise quantitative force measurements, due to the unknown value of the spring constant of the optical trap formed within the cell’s viscoelastic cytoplasm.Here, we describe amethod for utilizing optical tweezers for quantitative in vivo force measurements. The experimental protocol and the protocol for data analysis rely on two types of experiments, passive observation of the thermal motion of a trapped object inside a living cell, followed by observations of the response of the trapped object when subject to controlled oscillations of the optical trap. One advantage of this calibration method is that the size and refractive properties of the trapped object and the viscoelastic properties of its environment need not be known. We explain the protocol and demonstrate its use with experiments of trapped granules inside live S.pombe cells.
Original languageEnglish
Title of host publicationOptical Tweezers: Methods and Protocols
EditorsArne Gennerich
Number of pages24
Publication date2017
Pages513-536
Chapter20
ISBN (Print) 978-1493964192
DOIs
Publication statusPublished - 2017
SeriesMethods in Molecular Biology
Volume1486
ISSN1064-3745

Keywords

  • Optical Tweezers
  • Viscoelasticity
  • Cytoplasm
  • In Vivo
  • Force measurements
  • Spring constant

Cite this

Ritter, C. M., Maes, J., Oddershede, L., & Berg-Sørensen, K. (2017). Quantifying Force and Viscoelasticity Inside Living Cells Using an Active–Passive Calibrated Optical Trap. In A. Gennerich (Ed.), Optical Tweezers: Methods and Protocols (pp. 513-536). Methods in Molecular Biology, Vol.. 1486 https://doi.org/10.1007/978-1-4939-6421-5_20
Ritter, Christine M. ; Maes, Josep ; Oddershede, Lene ; Berg-Sørensen, Kirstine. / Quantifying Force and Viscoelasticity Inside Living Cells Using an Active–Passive Calibrated Optical Trap. Optical Tweezers: Methods and Protocols. editor / Arne Gennerich. 2017. pp. 513-536 (Methods in Molecular Biology, Vol. 1486).
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Ritter, CM, Maes, J, Oddershede, L & Berg-Sørensen, K 2017, Quantifying Force and Viscoelasticity Inside Living Cells Using an Active–Passive Calibrated Optical Trap. in A Gennerich (ed.), Optical Tweezers: Methods and Protocols. Methods in Molecular Biology, vol. 1486, pp. 513-536. https://doi.org/10.1007/978-1-4939-6421-5_20

Quantifying Force and Viscoelasticity Inside Living Cells Using an Active–Passive Calibrated Optical Trap. / Ritter, Christine M. ; Maes, Josep ; Oddershede, Lene; Berg-Sørensen, Kirstine.

Optical Tweezers: Methods and Protocols. ed. / Arne Gennerich. 2017. p. 513-536 (Methods in Molecular Biology, Vol. 1486).

Research output: Chapter in Book/Report/Conference proceedingBook chapterResearchpeer-review

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AB - As described in the previous chapters, optical tweezers have become a tool of precision for in vitro single-molecule investigations, where the single molecule of interest most often is studied in purified form in an experimental assay with a well-controlled fluidic environment. A well-controlled fluidic environment implies that the physical properties of the liquid, most notably the viscosity, are known and the fluidic environment can, for calibrational purposes, be treated as a simple liquid. In vivo, however, optical tweezers have primarily been used as a tool of manipulation and not so often for precise quantitative force measurements, due to the unknown value of the spring constant of the optical trap formed within the cell’s viscoelastic cytoplasm.Here, we describe amethod for utilizing optical tweezers for quantitative in vivo force measurements. The experimental protocol and the protocol for data analysis rely on two types of experiments, passive observation of the thermal motion of a trapped object inside a living cell, followed by observations of the response of the trapped object when subject to controlled oscillations of the optical trap. One advantage of this calibration method is that the size and refractive properties of the trapped object and the viscoelastic properties of its environment need not be known. We explain the protocol and demonstrate its use with experiments of trapped granules inside live S.pombe cells.

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BT - Optical Tweezers: Methods and Protocols

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Ritter CM, Maes J, Oddershede L, Berg-Sørensen K. Quantifying Force and Viscoelasticity Inside Living Cells Using an Active–Passive Calibrated Optical Trap. In Gennerich A, editor, Optical Tweezers: Methods and Protocols. 2017. p. 513-536. (Methods in Molecular Biology, Vol. 1486). https://doi.org/10.1007/978-1-4939-6421-5_20