Single-molecule magnetic tweezer analysis of topoisomerases

Kathryn H. Gunn, John F. Marko, Alfonso Mondragón*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapter

3 Scopus citations


Magnetic tweezers (MT) provide a powerful single-molecule approach to study the mechanism of topoisomerases, giving the experimenter the ability to change and read out DNA topology in real time. By using diverse DNA substrates, one can study different aspects of topoisomerase function and arrive at a better mechanistic understanding of these fascinating enzymes. Here we describe methods for the creation of three different DNA substrates used in MT experiments with topoisomerases: double-stranded DNA (dsDNA) tethers, “braided” (intertwined or catenated) DNA tether pairs, and dsDNA tethers with single-stranded DNA (ssDNA) regions. Additionally, we discuss how to build flow cells for bright-field MT microscopy, as well as how to noncovalently attach anti-digoxigenin to the coverslip surface for tethering digoxigenin-labeled DNAs. Finally, we describe procedures for the identification of a suitable DNA substrate for MT study and data collection.

Original languageEnglish (US)
Title of host publicationMethods in Molecular Biology
PublisherHumana Press Inc.
Number of pages14
StatePublished - 2018

Publication series

NameMethods in Molecular Biology
ISSN (Print)1064-3745


  • Bright-field microscopy
  • Flow cell
  • Functionalized DNA
  • Magnetic tweezers
  • Noncovalent antibody attachment
  • Single-molecule
  • Topoisomerases

ASJC Scopus subject areas

  • Molecular Biology
  • Genetics


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