Nanoscale phase separation in DSPC-cholesterol systems

Area of Science:

• Biochemistry
• Cell Biology
• Materials Science

Background:

• Eukaryotic cell membranes exhibit heterogeneous lipid arrangements with distinct domains.
• Cholesterol and saturated phospholipids form domains within a continuous phase of unsaturated phospholipids.
• The precise size and influencing factors of these lipid domains remain debated.

Purpose of the Study:

• To investigate the impact of phospholipid chain saturation and chain length on lipid domain size in model cell membranes.
• To determine how different lipid compositions affect nanoscale domain formation.
• To explore domain existence in phospholipid-cholesterol systems.

Main Methods:

• Utilized model membranes composed of specific phospholipid-cholesterol mixtures (DOPC-DSPC-Chol and POPC-DSPC-Chol).
• Employed steady-state fluorescence assays, including spectral shifts of DAN-PC and Förster resonance energy transfer (FRET).
• Applied an analytical model to estimate lipid domain sizes.

Main Results:

• Observed nanoscale lipid domains in both investigated ternary systems.
• Found that domains in the asymmetric POPC-based system were larger than those in the di-unsaturated DOPC-based system.
• Demonstrated domain existence in POPC-DSPC-Chol model membranes, a previously unreported finding.

Conclusions:

• Phospholipid chain saturation and length are critical determinants of lipid domain size in model membranes.
• Asymmetric lipid composition (POPC) leads to larger nanoscale domains compared to symmetric, di-unsaturated lipids (DOPC).
• This research provides new insights into the factors governing lipid domain organization at the nanoscale.