Lee's transient protonic capacitor cannot explain the surface proton current observed in bacteriorhodopsin purple...

Area of Science:

• Biophysics
• Membrane Biology
• Physical Chemistry

Background:

• James Lee proposed the transmembrane electrostatically localized proton (TELP) hypothesis to explain proton binding to bacteriorhodopsin.
• The TELP hypothesis utilizes a transient protonic capacitor model to describe forces at the membrane surface.

Purpose of the Study:

• To evaluate the validity of the TELP hypothesis in explaining proton interactions with purple membranes.
• To investigate the feasibility of a transient transmembrane potential supporting proton currents.

Main Methods:

• Analysis of purple membrane fragments' ability to sustain a transmembrane potential.
• Theoretical assessment of proton current flow under TELP conditions.
• Comparison with established models of proton-membrane interactions.

Main Results:

• Purple membrane fragments cannot maintain the necessary transient transmembrane potential for the TELP hypothesis.
• Even if a potential existed, it would not support the proton current reported by Heberle et al.
• Established models invoking interfacial water structure provide a more robust explanation for proton stabilization at membrane surfaces.

Conclusions:

• The TELP hypothesis, as currently formulated, is insufficient to explain proton binding to purple membranes.
• Future research on TELP should include experimental validation on lipid bilayer and biological membranes.