Figure 12.7.

The maximum solubility of cholesterol, ${\chi }_{\mathit{\text{chol}}}^{\ast }$, or the ratio (ceramide+choleserol)/(ceramide+cholesterol+PC) as a function of ceramide/(ceramide+POPC) ratio. Circles: ${\chi }_{\mathit{\text{chol}}}^{\ast }$, measured by COD activity assay. Triangle: The maximum solubility of ceramide in POPC bilayers determined by optical microscopy measurement. The dashed line is the theoretical ${\chi }_{\mathit{\text{chol}}}^{\ast }$ curve with the assumption that one ceramide molecule displaces one cholesterol from the bilayer phase into the cholesterol crystal phase. Squares: the ratio (ceramide+choleserol)/(ceramide+cholesterol+PC) at the cholesterol solubility limits.