Interfacial water molecules at biological membranes: Structural features and role for lateral proton diffusion

Area of Science:

• Biophysics
• Computational Chemistry

Background:

• Proton transport across biological membranes is vital for energy conversion.
• Understanding proton behavior at the water/lipid interface is key to bioenergetics.

Purpose of the Study:

• To investigate the behavior and interactions of excess protons at phosphatidylcholine bilayer interfaces.
• To elucidate the mechanisms underlying proton mobility at membrane interfaces.

Main Methods:

• Ab initio molecular dynamics simulations were employed.
• Simulations focused on proton transfer along two phosphatidylcholine bilayers.

Main Results:

• Excess protons preferentially reside at the water/membrane interface.
• Protons interact with both phosphate head groups and interfacial water molecules.
• Interfacial water molecules exhibit orientation relative to the lipid bilayers.

Conclusions:

• The specific interactions between protons and oriented interfacial water molecules likely explain observed proton mobility.
• This finding provides insights into proton transfer mechanisms at biological interfaces.