Sphingomyelin-cholesterol domains in phospholipid membranes: atomistic simulation

Area of Science:

• Biophysics
• Computational Biology
• Materials Science

Background:

• Cell membranes are complex lipid bilayers with distinct domains.
• Sphingomyelin and cholesterol form liquid-ordered domains that influence membrane properties.
• Understanding these domain interactions is crucial for cell membrane function.

Purpose of the Study:

• To investigate the atomic-level interactions between sphingomyelin-cholesterol domains and dioleylposphatidylcholine (DOPC) bilayers.
• To quantify the impact of these domains on lipid packing and bilayer thickness.
• To develop and validate a computational method for analyzing ternary lipid mixtures.

Main Methods:

• Atomic-level molecular dynamics simulations of a nanoscopic lipid system.
• Calculation of order parameters and area per molecule.
• Development of a Voronoi tessellation algorithm for area per molecule analysis.
• Computation of electron density profiles and bilayer thickness differences.

Main Results:

• Calculated areas per sphingomyelin and cholesterol match previous simulations.
• Liquid-ordered domains influence DOPC bilayer packing up to ~8 nm.
• Significant differences in bilayer thickness between the domain and surrounding regions were observed.

Conclusions:

• Sphingomyelin-cholesterol domains exert long-range effects on lipid packing in DOPC bilayers.
• The computational methods provide accurate insights into lipid domain behavior.
• Simulation results are consistent with experimental atomic force microscopy data, validating the model.