Manipulation of Force Geometry using Optical Tweezers Reveals Novel Features of Biomolecular Interactions

Serapion Pyrpassopoulos, Allison M. Gicking, Taylor M. Zaniewsky, Henry Shuman, William Hancock, E. Michael Ostap

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Optical tweezers have greatly impacted the development of mechanobiology by enabling high precision subpiconewton measurements of mechanical forces developed by force generating proteins, called molecular motors, at the single-molecule level. Molecular motors, such as kinesins hydrolyze ATP to generate force (<10 pN) and transport in a directional manner intracellular cargoes along cytoskeletal filamentous tracks called microtubules. The force developed by kinesins have been mainly studied using the “single-bead” assay, where an optically trapped bead is pulled by a bead-attached kinesin molecule as it steps along a surface immobilized microtubule. This assay, besides forces parallel to the long axis of the filament on which the kinesin processes, forces perpendicular to the filament due to the bead interacting with the underlying microtubule. These perpendicular forces, which cannot be directly measured, can accelerate the detachment of the molecular motor from its filamentous track. An alternative approach is the “three-bead” assay, in which the vertical force component is minimized, and the total opposing force is mainly parallel to the microtubule. Experiments with kinesin show that microtubule attachment durations can be highly variable and up to 10-fold longer in the three-bead assay, compared to the single-bead. Thus, the ability of kinesin to bear mechanical load and remain attached to microtubules depends on the geometry of forces across the microtubule. Our work shows the importance for the development of optical trapping assays where the direction of the force vector can be very finely controlled and measured when studying the mechanical strength of biomolecular interactions.

Original languageEnglish (US)
Title of host publicationOptical Trapping and Optical Micromanipulation XX
EditorsKishan Dholakia, Gabriel C. Spalding
ISBN (Electronic)9781510665125
StatePublished - 2023
EventOptical Trapping and Optical Micromanipulation XX 2023 - San Diego, United States
Duration: Aug 20 2023Aug 24 2023

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceOptical Trapping and Optical Micromanipulation XX 2023
Country/TerritoryUnited States
CitySan Diego

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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