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Related Experiment Videos

Diffusion potential cascade. Convenient detection of transferable membrane pores.

L M Loew, I Rosenberg, M Bridge

    Biochemistry
    |February 15, 1983
    PubMed
    Summary

    Gramicidin channels collapse liposome membrane potential by facilitating potassium ion flow. This process, involving gramicidin binding and channel formation, can be monitored using fluorescent dyes, aiding membrane pore detection.

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    Area of Science:

    • Biophysics
    • Membrane Biology
    • Liposome Research

    Background:

    • Valinomycin creates stable potassium diffusion potentials in multilamellar liposomes.
    • Gramicidin acts as a nonselective channel to collapse these potentials.

    Purpose of the Study:

    • To investigate the complex kinetics of gramicidin-mediated collapse of liposome membrane potential.
    • To establish a method for detecting and characterizing membrane pores using voltage-sensitive dyes.

    Main Methods:

    • Utilized multilamellar liposomes with valinomycin-mediated K+ diffusion potentials.
    • Introduced gramicidin to induce potential collapse and analyzed the kinetics.
    • Employed 3,3'-diethylthiodicarbocyanine iodide [diS-C2-(5)] as a voltage-sensitive fluorescent dye.

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    Main Results:

    • Identified key processes in potential collapse: gramicidin binding, dimerization, ion flux, and bilayer-to-bilayer propagation.
    • Determined that gramicidin dissociation is rate-limiting at high concentrations, while ion flux limits at low concentrations.
    • Observed voltage dependence in K+ gradient collapse at low gramicidin concentrations.

    Conclusions:

    • The study provides a detailed kinetic model for gramicidin-mediated membrane potential collapse in liposomes.
    • Demonstrated a simple, dye-based method for detecting and characterizing membrane pores.
    • Highlights the influence of liposome composition, size, and ion concentrations on the process.