Dynamic single-molecule force spectroscopy using optical tweezers and nanopores

Nadanai Laohakunakorn, Oliver Otto, Sebastian Sturm, Klaus Kroy, Ulrich F. Keyser*

*Corresponding author for this work

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


Single-molecule force spectroscopy is a powerful technique for studying the detailed behaviour of biopolymers such as DNA and proteins: by applying pN-scale forces to individual molecules, properties such as conformations, folding pathways, and intermolecular interaction strengths can be determined. Traditionally these studies have been carried out under static tension. The dynamic response of polymers to a sudden change in force is experimentally more challenging as the polymer is often coupled to an external molecular handle, which suppresses important physics at short (ms) timescales. Here we use a nanopore to electrically control the application of force to the end of a double-stranded DNA molecule; the other end of the molecule is attached to a bead held in an optical trap. By shutting off the voltage, the fast relaxation dynamics of the free polymer end can be studied. We observe for the first time an enhanced viscous friction which arises from the rapid internal contraction of the DNA, which is fully explained by theory. These studies pave the way for new dynamic force spectroscopy experiments, such as investigations of tension propagation along biomolecules, which has applications for both polymer theory as well as biological systems such as the cytoskeleton where dynamic tension can affect cellular response.

Original languageEnglish
Title of host publicationOptical Trapping and Optical Micromanipulation X
Publication statusPublished - 12 Sep 2013
EventOptical Trapping and Optical Micromanipulation X - San Diego, CA, United States
Duration: 25 Aug 201329 Aug 2013


ConferenceOptical Trapping and Optical Micromanipulation X
CountryUnited States
CitySan Diego, CA


  • DNA
  • dynamic force spectroscopy
  • nanopore
  • optical tweezers
  • relaxation dynamics
  • single molecule


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