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Proceedings Paper

Force measurements with optical tweezers inside living cells
Author(s): Josep Mas; Arnau Farré; Jordi Sancho-Parramon; Estela Martín-Badosa; Mario Montes-Usategui
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Paper Abstract

The force exerted by optical tweezers can be measured by tracking the momentum changes of the trapping beam, a method which is more general and powerful than traditional calibration techniques as it is based on first principles, but which has not been brought to its full potential yet, probably due to practical difficulties when combined with high-NA optical traps, such as the necessity to capture a large fraction of the scattered light. We show that it is possible to measure forces on arbitrary biological objects inside cells without an in situ calibration, using this approach. The instrument can be calibrated by measuring three scaling parameters that are exclusively determined by the design of the system, thus obtaining a conversion factor from volts to piconewtons that is theoretically independent of the physical properties of the sample and its environment. We prove that this factor keeps valid inside cells as it shows good agreement with other calibration methods developed in recent years for viscoelastic media. Finally, we apply the method to measuring the stall forces of kinesin and dynein in living A549 cells.

Paper Details

Date Published: 16 September 2014
PDF: 9 pages
Proc. SPIE 9164, Optical Trapping and Optical Micromanipulation XI, 91640U (16 September 2014); doi: 10.1117/12.2061919
Show Author Affiliations
Josep Mas, Univ. de Barcelona (Spain)
Univ. of St. Andrews (United Kingdom)
Arnau Farré, Univ. de Barcelona (Spain)
Impetux Optics S.L. (Spain)
Jordi Sancho-Parramon, Univ. de Barcelona (Spain)
Institut Ruđer Bošković (Croatia)
Estela Martín-Badosa, Univ. de Barcelona (Spain)
Mario Montes-Usategui, Univ. de Barcelona (Spain)
Impetux Optics S.L. (Spain)

Published in SPIE Proceedings Vol. 9164:
Optical Trapping and Optical Micromanipulation XI
Kishan Dholakia; Gabriel C. Spalding, Editor(s)

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