Cardiolipin vesicles can accommodate cholesterol up to 0.80 mole fraction, i.e. one molecule per cardiolipin fatty acid chain

AbstractCardiolipin-cholesterol interactions were studied by time-resolved fluorescence spectroscopy with 1,6-diphenyl-1, 3,5-hexatriene as probe. The residual anisotropy parameter, r∞ (reflecting the fatty acid chain packing), was measured in the liquid crystalline phase as a function of cholesterol addition. Two main results are reported: (i) a slight increase of the order parameter, S, computed from the r∞ value as S = (r∞/r0)12, in the physiological concentration range of cholesterol; (ii) a sharp enhancement of S from a cholesterol mole fraction (X̄chl) of 0.20 and up to X̄chl of 0.80. This is in contrast to unsaturated kcithin systems for which a continuous increase of the order parameter was monitored, culminating at X̄chl = 0.50, the wellknown maximum level of incorporation of cholesterol into lecithin model membranes