Molecular dynamics simulations of mixed acidic/zwitterionic phospholipid bilayers

Area of Science:

• Biochemistry
• Molecular Biology
• Computational Biophysics

Background:

• Anionic lipids are crucial for cell membrane function, influencing protein interactions and cellular signaling.
• Phospholipid bilayers serve as vital model systems for studying membrane structure and dynamics.

Purpose of the Study:

• To investigate lipid-protein interactions and clustering in pure and mixed anionic lipid bilayers using molecular dynamics simulations.
• To analyze the impact of monovalent ions (Na+) on salt-bridge formation and lipid clustering.

Main Methods:

• 200-ns molecular dynamics (MD) simulations of pure (DMPC, DMPG) and mixed equimolar (DMPC/DMPG, DMPC/DMPS, DMPC/DMPA) phospholipid bilayers.
• Analysis of intra- and intermolecular interaction patterns within the bilayers.
• Investigation of sodium ion (Na+) effects on salt-bridge formation and lipid clustering.

Main Results:

• DMPS and DMPA lipids exhibit preferential self-clustering, distinct from DMPC molecules in mixed bilayers.
• Higher numbers of Na+-mediated clusters were observed with DMPS compared to DMPG and DMPA.
• Observed lipid clustering patterns correlate with experimentally reported phase separations in DMPC/DMPS and DMPC/DMPA bilayers.

Conclusions:

• Lipid clustering, particularly of DMPS and DMPA, is a key factor driving phase separation in mixed phospholipid bilayers.
• Molecular dynamics simulations provide valuable insights into the molecular mechanisms underlying membrane phase behavior.
• Understanding these interactions is critical for elucidating cell membrane organization and function.