Single molecule tracking of a semiflexible polyelectrolyte chain in solvent under uniform electroosmotic flows

Sunghun Choung, Myung Suk Chun, Chongyoup Kim

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Direct single molecule tracking of a polyelectrolyte chain by using fluorescence microscopy has allowed both the assumptions and the predictions of relevant theories to be tested. The center-ofmass displacement is determined as a function of the time that elapses between images, where the radius of gyration can be estimated from a first moment of the image distribution. The translational self-diffusion for the molecule is an ensemble property of the mean square displacement (MSD) with lag time in each trajectory. Experimentally viable two-dimensional imaging of semiflexible polyelectrolyte was performed on a fluorescein-labeled xanthan chain in electroosmosis-driven uniform flow fields. The radius of gyration was almost constant under variations of the electroosmotic flow velocity determined by an externally applied electric field. We try to develop a correction of the MSD in flow field, taking into account the velocity fluctuations. Its advantage allows acquiring the linear fit for the MSD vs lag time, for a good estimate of the translational diffusion. Increasing behavior of the diffusion with increasing fluid velocity ensures a quadratic equation fit, which should connect with the convective effect. Our results exhibit a screening effect such that strong screening caused by a high ionic concentration leads to higher diffusion due to the compact chain conformation. Considering the uniform flow serves as a basis for understanding the behavior of individual polyelectrolyte chains under controlled fluidic flow in confined spaces.

Original languageEnglish
Pages (from-to)2847-2854
Number of pages8
JournalJournal of the Korean Physical Society
Issue number4
Publication statusPublished - 2011 Oct 14


  • Chain conformation
  • Polyelectrolyte
  • Rheology
  • Single molecule tracking
  • Translational diffusion
  • Uniform flow

ASJC Scopus subject areas

  • General Physics and Astronomy


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