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Single-Molecule Measurements of Topoisomerase Activity with Magnetic Tweezers

  • Yeonee Seol
  • Keir C. NeumanEmail author
Protocol
Part of the Methods in Molecular Biology book series (MIMB, volume 778)

Abstract

Magnetic tweezers provide a versatile tool enabling the precise application of force and torque on ­individual biomolecules. These properties make magnetic tweezers uniquely suited for the study of DNA topology and topoisomerases at the single-molecule level. Single-molecule approaches, which are complementary to ensemble biochemical and structural approaches, have provided remarkable insights into the mechanisms of topoisomerase activity and interactions with DNA. Here, we describe how to make single-molecule measurements of topoisomerase activity with a magnetic tweezers instrument. We provide detailed instructions for preparing and characterizing DNA substrates, flow cells, and supercoilable DNA tethers. We then describe magnetic tweezers measurements of supercoil relaxation by single topoisomerases.

Key words

Magnetic tweezers Single molecule DNA topology DNA topoisomerase 

Notes

Acknowledgments

The authors would like to thank Marie-Paule Strub, Vincent Croquette, Jean-Francois Allemand, Timothée Lionnet, Omar Saleh, and David Bensimon for assistance and enlightening discussions and Grace Liou for critical reading of the manuscript. This research was supported by the Intramural Research Program of the National Heart, Lung, and Blood Institute, National Institutes of Health.

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Copyright information

© Springer Science+Business Media, LLC 2011

Authors and Affiliations

  1. 1.Laboratory of Molecular BiophysicsNational Heart, Lung, and Blood Institute, National Institutes of HealthBethesdaUSA

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