Some properties of particles of egg-yolk phosphatidylcholine and cholesterol

Abstract

Some physicochemical properties of particles of phosphatidylcholine and cholesterol, produced by ultrasonication of their aqueous dispersions in varying proportions and concentrations were investigated. Cholesterol altered the micellar characteristics according to its proportion. S 20, w values increased incrementally from 2.53 for phosphatidylcholine alone to 15.65 for particles containing the highest proportion and concentration of solubilized cholesterol (0.28 g/100 ml of each lipid). Similarly, particle weight increased from 3 × 10 6 to 7.12 × 10 7, axial ratios from 3.9 (discs) and 3.3 (rods) to 28.0 (discs) and 13.0 (rods), the viscosity shape factor, ν, from 3.9 to 20.7, water of hydration decreased from 0.26 g H 2O/g lipid to 0.22 g H 2O/g lipid and the number of monomers within each particle ranged from 4000 to 84,000. Ultrasonication at 50° produced greater lipid retention as colloid at the limiting 1:2 molar proportion, with lower values of S 20, w, particle weight, axial ratio, ν, and water of hydration than when ultrasonicated at 25°. Cholesterol thus considerably alters particles of phosphatidylcholine making them heavier, more asymmetrical, less hydrated and more rigid.