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Updated: May 10, 2026
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Combining Single-molecule Manipulation and Imaging for the Study of Protein-DNA Interactions
Published on: August 27, 2014
Single-molecule fluorescence imaging of DNA at a potential-controlled interface
Eric M Peterson1, Joel M Harris
1Department of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112-0850, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|June 8, 2013
Summary
Electrostatic interactions control interfacial phenomena. This study shows DNA molecules accumulate near a polarized electrode, influenced by applied potential and ionic strength, revealing insights into charge screening.
Area of Science:
- Interfacial Electrochemistry
- Biophysics
- Materials Science
Background:
- Interfacial electrostatic interactions between polyelectrolytes and charged surfaces are crucial for biosensors, soil science, and material fabrication.
- Understanding these interactions is key to controlling interfacial phenomena.
Purpose of the Study:
- To investigate the behavior of plasmid DNA near a polarized indium tin oxide (ITO) electrode.
- To quantify the influence of applied potential and ionic strength on DNA accumulation at the interface.
Main Methods:
- Utilized total-internal-reflection fluorescence microscopy to monitor interfacial DNA in situ.
- Employed a model polyelectrolyte: 15 kbp fluorescently labeled plasmid DNA.
- Applied electrochemical potentials to an ITO electrode and varied ionic strength.
Main Results:
- Observed a 2-order-of-magnitude increase in interfacial DNA population at +0.8 V vs. Ag/AgCl.
- DNA molecules remained mobile at the interface, with diffusion coefficients similar to free solution.
- Ionic strength significantly affected potential sensitivity; a 300 mV change caused a 20% increase at 30 mM and a 25-fold increase at 300 μM electrolyte.
Conclusions:
- DNA accumulation is driven by electrostatic interactions with the polarized ITO surface.
- Models suggest low net charge on DNA and significant counterion screening of excess charge.
- Results provide a foundation for understanding and manipulating polyelectrolyte behavior at interfaces.
