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Chiu Tai Andrew Wong1, M Muthukumar

  • 1Department of Polymer Science and Engineering, University of Massachusetts, Amherst, Massachusetts 01003, USA.

The Journal of Chemical Physics
|August 7, 2010
PubMed
Summary

We studied how sodium poly(styrene sulfonate) polymers move through alpha-hemolysin pores. We found that pH gradients control successful polymer translocation, impacting protein-polymer interactions.

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Area of Science:

  • Biophysics
  • Nanotechnology
  • Polymer Science

Background:

  • Single-molecule analysis of polymer translocation through nanopores is crucial for understanding molecular interactions.
  • The alpha-hemolysin pore provides a model system for studying transport phenomena at the nanoscale.

Purpose of the Study:

  • To investigate the ionic current blockages caused by sodium poly(styrene sulfonate) polymers in an alpha-hemolysin pore.
  • To elucidate the molecular mechanisms underlying two-level current blockages and successful translocation events.
  • To explore the influence of pH gradients on polymer translocation dynamics.

Main Methods:

  • Measuring ionic current blockages using single molecules of sodium poly(styrene sulfonate) passing through an alpha-hemolysin pore under an electric field.
  • Analyzing blockage event statistics across varying polymer lengths, applied voltages, and pH conditions.
  • Developing a stochastic theory for polymer translocation with tunable polymer-pore interactions.

Main Results:

  • Identified distinct ionic current blockage levels (one or two) corresponding to polymer interactions within the pore.
  • Demonstrated that not all blockages represent successful translocation events.
  • Showed that pH gradients significantly tune the propensity of successful translocation by altering protein-polymer interactions through amino acid residue protonation.

Conclusions:

  • The study reveals that pH-dependent changes in protein-polymer interactions govern successful polymer translocation through the alpha-hemolysin pore.
  • A theoretical model was developed that accurately captures experimental observations of polymer translocation dynamics.
  • Findings offer insights into controlling nanoscale transport for potential applications in sensing and separation.