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Proton diffusion at phospholipid assemblies
1Contribution from the Department of Chemistry, University of Warwick, Coventry CV4 7AL, UK.
Journal of the American Chemical Society
|March 7, 2002
Summary
A new scanning electrochemical microscopy proton feedback method reveals significant lateral proton diffusion in acidic phospholipid monolayers (DPPS). Zwitterionic (DPPC) monolayers show no detectable proton diffusion, highlighting the role of acid-base properties.
Area of Science:
- Electrochemistry
- Surface Science
- Biophysics
Background:
- Phospholipid monolayers at interfaces are crucial in biological systems.
- Understanding proton dynamics at these interfaces is key to cellular processes.
- Current methods for studying interfacial proton diffusion are limited.
Purpose of the Study:
- To develop a novel scanning electrochemical microscopy (SECM) proton feedback method.
- To investigate lateral proton diffusion in phospholipid monolayers.
- To compare proton diffusion in acidic (DPPS) versus zwitterionic (DPPC) monolayers.
Main Methods:
- Utilized a "submarine" ultramicroelectrode (UME) in a Langmuir trough.
- Electrogenerated a base to perturb and detect proton concentrations.
- Developed a numerical model accounting for interfacial acid-base properties.
Main Results:
- Demonstrated significant lateral proton fluxes in dipalmitoyl-L-alpha-phosphatidyl-L-serine (DPPS) monolayers.
- Observed a lower lateral proton diffusion coefficient in DPPS compared to bulk solution.
- Found no detectable lateral proton diffusion in dipalmitoyl-L-alpha-phosphatidylcholine (DPPC) monolayers.
Conclusions:
- The developed SECM proton feedback method is effective for studying interfacial proton diffusion.
- Acid-base properties of phospholipids significantly influence interfacial proton transport.
- Lateral proton diffusion is substantial in acidic phospholipids but negligible in zwitterionic ones.
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