Portal de Periódicos da CAPES

Sphingomyelin/Phosphatidylcholine/Cholesterol Phase Diagram: Boundaries and Composition of Lipid Rafts

2003; Elsevier BV; Volume: 85; Issue: 4 Linguagem: Inglês

10.1016/s0006-3495(03)74664-5

1542-0086

Rodrigo F.M. de Almeida, А.А. Федоров, Manuel Prieto,

Surfactants and Colloidal Systems

The ternary system palmitoylsphingomyelin (PSM)/palmitoyloleoylphosphatidylcholine (POPC)/cholesterol is used to model lipid rafts. The phase behavior of the three binary systems PSM/POPC, PSM/cholesterol, and POPC/cholesterol is first experimentally determined. Phase coexistence boundaries are then determined for ternary mixtures at room temperature (23°C) and the ternary phase diagram at that temperature is obtained. From the diagram at 23°C and the binary phase diagrams, a reasonable expectation is drawn for the ternary phase diagram at 37°C. Several photophysical methodologies are employed that do not involve detergent extraction, in addition to literature data (e.g., differential scanning calorimetry) and thermodynamic rules. For the ternary phase diagrams, some tie-lines are calculated, including the one that contains the PSM/POPC/ cholesterol 1:1:1 mixture, which is often used in model raft studies. The diagrams here described are used to rationalize literature results, some of them apparently discrepant, and to discuss lipid rafts within the framework of liquid-ordered/liquid-disordered phase coexistence.