Cardiolipin vesicles can accommodate cholesterol up to 0.80 mole fraction, i.e. one molecule per cardiolipin fatty acid chain.
Cardiolipin-cholesterol interactions were studied by time-resolved fluorescence spectroscopy with 1,6-diphenyl-1,3,5-hexatriene as probe. The residual anisotropy parameter, r infinity (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 infinity value as S = (r infinity/r0)1/2, in the physiological concentration range of cholesterol; (ii) a sharp enhancement of S from a cholesterol mole fraction (X chl) of 0.20 and up to X chl of 0.80. This is in contrast to unsaturated lecithin systems for which a continuous increase of the order parameter was monitored, culminating at X chl = 0.50, the well-known maximum level of incorporation of cholesterol into lecithin model membranes.
D000818:Animals; D002308:Cardiolipins; D002417:Cattle; D002784:Cholesterol; D008051:Lipid Bilayers; D010713:Phosphatidylcholines
D002308:Cardiolipins; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine