Anomalous surface diffusion of protons on lipid membranes

Area of Science:

• Biophysics
• Computational Chemistry
• Membrane Biophysics

Background:

• Proton behavior near lipid membranes is vital for cellular energy transduction.
• Understanding proton energetics and mobility is key to cellular function.

Purpose of the Study:

• To investigate the energetics and mobility of excess protons near a solvated DMPC lipid bilayer.
• To elucidate the mechanism of proton surface diffusion using advanced simulation techniques.

Main Methods:

• Classical molecular dynamics simulations incorporating the Grotthuss proton shuttling mechanism.
• Simulations performed on a solvated DMPC bilayer at 323 K.

Main Results:

• Calculated a proton surface affinity of -13.0 ± 0.5 kJ/mol.
• Observed strong proton interactions with lipid headgroup and carbonyl oxygens.
• Characterized anomalous proton surface diffusion: initial subdiffusion followed by superdiffusion.
• Identified diffusion origin in restricted surface-bound states and occasional bulk-mediated diffusion.

Conclusions:

• Proton surface diffusion is anomalous and depends on membrane-bound states and bulk interactions.
• Findings may resolve discrepancies in previously reported diffusion coefficients.
• Speculated sensitivity of diffusion to specific membrane conditions impacting energy machinery.