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Quantifying proton-induced membrane polarization in single biomimetic giant vesicles
Ran Tivony1, Marcus Fletcher1, Ulrich F Keyser1
1Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom.
Biophysical Journal
|June 1, 2022
Summary
Researchers developed a new method to measure proton flux across lipid vesicles. This technique quantifies proton motive force, aiding artificial cell development and understanding acid transport across membranes.
Area of Science:
- Biophysics
- Membrane Biophysics
- Artificial Cell Research
Background:
- Proton gradients are crucial for cellular energy and transport.
- Studying membrane proteins in isolation requires precise measurements of proton flux.
- Artificial cell models like proteo-giant unilamellar vesicles are valuable research tools.
Purpose of the Study:
- To develop and present a method for directly quantifying proton flux across single lipid vesicles.
- To investigate the relationship between proton permeation, transmembrane potential, and the chemical nature of the conjugated anion.
- To understand the mechanisms of proton transport in artificial cell systems.
Main Methods:
- Utilized single cell-sized lipid vesicles (proteo-giant unilamellar vesicles).
- Modulated electrochemical gradients across the lipid bilayer.
- Directly quantified proton flux and measured transmembrane potential development.
Main Results:
- Demonstrated a direct association between proton permeation and transmembrane potential.
- Showed that formic acid permeates as both H+ (≈0.2) and neutral acid (≈0.8).
- Strong acids (HCl, HNO3) primarily permeate as H+, generating higher proton motive force (pmf) (14.2 mV) compared to formic acid (1.3 mV).
Conclusions:
- The developed approach enables accurate measurement of proton flux and pmf in artificial cell models.
- Findings provide insights into the differential transport mechanisms of various acids across lipid bilayers.
- This work will advance the development of proton gradient-driven transport in synthetic cells and improve understanding of vital acid transport.
