Structural and dynamical surface properties of phosphatidylethanolamine containing membranes

Area of Science:

• Biophysics
• Lipid Bilayer Dynamics
• Surface Chemistry

Background:

• Phospholipids like dimyristoylphosphatidylethanolamine (DMPE) and dimyristoylphosphatidylcholine (DMPC) are crucial membrane components.
• Understanding their hydration and interfacial properties is key to membrane function.

Purpose of the Study:

• To investigate the hydration differences between solid DMPE and DMPC.
• To elucidate the factors limiting DMPE hydration and its impact on molecular mobility.
• To explore the influence of phospholipid mixtures on dipole potentials and protein adsorption.

Main Methods:

• Infrared spectroscopy to analyze phosphate group hydration.
• Monolayer studies to assess dipole potentials and surface pressure.
• Protein adsorption experiments to evaluate interfacial properties.

Main Results:

• DMPE hydration shows a negligible shift in phosphate stretching frequency, unlike DMPC, indicating minimal disruption of the solid lattice.
• Strong lateral interactions between NH3 and PO2- groups in solid PEs persist upon hydration, hindering polar head reorientation and increasing energy for P-N dipole translocation.
• Mixtures of PCs and PEs exhibit varied dipole potentials and hydration based on acyl chain saturation, impacting P-N group reorientation.
• Despite low hydration, DMPE interfaces possess excess surface free energy, enabling protein adsorption, albeit at a slower rate than DMPC.

Conclusions:

• DMPE hydration is limited by persistent lateral interactions, affecting polar head mobility.
• Phospholipid chain interactions and saturation significantly influence membrane dipole potentials and hydration.
• DMPE's interfacial properties, characterized by excess surface free energy, facilitate protein adsorption despite limited water content.