Figure 3.

Effect of the ceramide analogs on the melting of PSM-rich domains in POPC bilayers. 7SLPC-induced fluorescence quenching of tPA as a function of temperature was measured in multilamellar vesicles with 50 μM final lipid concentration. The vesicles were composed of POPC/PSM (82/18 mol %), POPC/PSM/CHL (70/15/15 mol %), and POPC/PSM/Cer (70/15/15 mol %). F/F₀ was defined as the relative fluorescence intensity of tPA in the F samples that contained both 7SLPC (replacing 50% of POPC) and tPA (1 mol %) over the intensity in the F₀ samples that contained tPA (1 mol %) but no 7SLPC. tPA-quenching revealed that each of the ceramide analogs was able to thermally stabilize the PSM-rich domains in fluid POPC bilayers. However, compared with CHL, only 16:1-, 18:1-, and 20:1-PCer were more pronounced in their ability to increase the end-melting temperature of the PSM-rich domains. As a reference to the relative changes in the F/F₀ between the different mixtures, the initial F/F₀ value is given for each measurement. Representative curves of two independently repeated experiments are shown.