Interaction of salt with ether- and ester-linked phospholipid bilayers

Area of Science:

• Biophysics
• Membrane Biophysics
• Computational Biophysics

Background:

• Archaeal plasma membranes feature ether-linked phospholipids, unlike bacterial and eukaryotic membranes which primarily use ester-links.
• This structural difference in lipid headgroup-tail linkage influences model bilayer properties.

Purpose of the Study:

• To investigate the effects of salt on the structure of ether-linked lipid bilayers.
• To compare the behavior of an ether-linked lipid bilayer (HOPC) with its ester-linked analog (POPC) in a NaCl solution.

Main Methods:

• Utilized molecular dynamics simulations to analyze equilibrium properties of POPC and HOPC bilayers.
• Developed a protocol to define the lipid-water interfacial boundary and analyze salt distribution.
• Applied Gouy-Chapman theory to interpret salt distribution near the bilayer interface.

Main Results:

• The ether-linked HOPC bilayer headgroup region adsorbed fewer ions (Na+) compared to the ester-linked POPC bilayer.
• The Debye screening length was approximately 10% shorter in the HOPC system.
• HOPC bilayers exhibited excess solvent in the headgroup region, with water molecules showing stronger coordination and reduced mobility, correlating with lower Na+ density.

Conclusions:

• Ether-linked lipid bilayers demonstrate a lower binding affinity for Na+ ions compared to ester-linked bilayers.
• The distinct hydration and ion-binding properties of ether-linked lipids influence the electrostatic environment and structural characteristics of archaeal membranes.