Studies on the anomalous thermotropic behavior of aqueous dispersions of dipalmitoylphosphatidylcholine-cholesterol mixtures.
Examination of the thermotropic behavior of aqueous dispersions of dipalmitoylphosphatidylcholine-cholesterol mixtures by high-sensitivity scanning calorimetry has revealed that the phospholipid gel to liquid-crystalline phase transition consists of two components. One, a relatively sharp transition centered at 39.6-40.7 degrees C, exhibits a transition enthalpy change which decreases linearly with increasing cholesterol content, approaching zero at a cholesterol content of about 25 mol %. The other, a broad, lower intensity transition centered at approximately 41.5 degrees C for cholesterol concentrations of 20 mol %, displays an enthalpy change which is maximal at about 20-25 mol % cholesterol and which decreases as the cholesterol content decreases to zero or increases above 25 mol %. The origin of these two transitions is discussed in terms of a separation of these lipid mixtures into cholesterol-rich and cholesterol-poor domains.
D002152:Calorimetry, Differential Scanning; D002784:Cholesterol; D008567:Membranes, Artificial; D008954:Models, Biological; D011663:Pulmonary Surfactants; D013816:Thermodynamics
D008567:Membranes, Artificial; D011663:Pulmonary Surfactants; D002784:Cholesterol