Modular stitching to image single-molecule DNA transport

Juan Guan, Bo Wang, Sung Chul Bae, Steve Granick

Research output: Contribution to journalArticlepeer-review


For study of time-dependent conformation, all previous single-molecule imaging studies of polymer transport involve fluorescence labeling uniformly along the chain, which suffers from limited resolution due to the diffraction limit. Here we demonstrate the concept of submolecular single-molecule imaging with DNA chains assembled from DNA fragments such that a chain is labeled at designated spots with covalently attached fluorescent dyes and the chain backbone with dyes of different color. High density of dyes ensures good signal-to-noise ratio to localize the designated spots in real time with nanometer precision and prevents significant photobleaching for long-time tracking purposes. To demonstrate usefulness of this approach, we image electrophoretic transport of λ-DNA through agarose gels. The unexpected pattern is observed that one end of each molecule tends to stretch out in the electric field while the other end remains quiescent for some time before it snaps forward and the stretch-recoil cycle repeats. These features are neither predicted by prevailing theories of electrophoresis mechanism nor detectable by conventional whole-chain labeling methods, which demonstrate pragmatically the usefulness of modular stitching to reveal internal chain dynamics of single molecules.

Original languageEnglish (US)
Pages (from-to)6006-6009
Number of pages4
JournalJournal of the American Chemical Society
Issue number16
StatePublished - Apr 24 2013

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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