Absence of fluid-ordered/fluid-disordered phase coexistence in ceramide/POPC mixtures containing cholesterol.

M. FIDORRA; L. DUELUND; C. LEIDY; A.C. SIMONSEN; LUIS A. BAGATOLLI

BIOPHYSICAL JOURNAL

CELL PRESS

Lugar: United States; Año: 2006 vol. 90 p. 4437 - 4437

0006-3495

he effect of temperature on the lateral structure of lipid bilayers composed of porcine brain ceramide and 1-palmitoyl 2-oleoyl-phosphatidylcholine (POPC), with and without addition of cholesterol, were studied using differential scanning calorimetry, Fourier transformed infrared spectroscopy, atomic force microscopy, and confocal/two-photon excitation fluorescence microscopy (which included LAURDAN generalized polarization function images). A broad gel/fluid phase coexistence temperature regime, characterized by the presence of micrometer-sized gel-phase domains with stripe and flowerlike shapes, was observed for different POPC/ceramide mixtures (up to approximately 25 mol % ceramide). This observed phase coexistence scenario is in contrast to that reported previously for this mixture, where absence of gel/fluid phase coexistence was claimed using bulk LAURDAN generalized polarization (GP) measurements. We demonstrate that this apparent discrepancy (based on the direct comparison bet