Interaction of Ubiquinone-10 with Dipalmitoylphosphatidylcholine and Their Formation of Small Dispersed Particles

Abstract

Stable aqueous dispersions of ubiquinone-10 (UQ) were obtained by cosonication with dipalmitoylphosphatidylcholine (DPPC) in the UQ mole fraction range 0.1–0.7. To clarify the dispersal mechanism, the dispersed particles were characterized, and the interaction between UQ and DPPC was investigated using several physicochemical techniques. Dynamic light scattering (DLS) measurements showed that the diameter of the dispersed particles was 50–70 nm. A limited amount of UQ was incorporated into DPPC bilayer membranes (approximately 5 mol%). The trapped aqueous volume inside the particles was determined fluorometrically using the aqueous space marker calcein, and the volume in the UQ/DPPC particles decreased remarkably with the addition of UQ into small unilamellar vesicles of DPPC. The decline in the fraction of vesicular particles was also confirmed by fluorescence quenching of N-dansylhexadecylamine in the DPPC membrane by the addition of the quencher CuSO₄. These results indicate that the excess UQ separated from the DPPC bilayers is stabilized as emulsion particles by the DPPC surface monolayer.

Key Words:

• Dipalmitoylphosphatidylcholine
• Dispersion
• Particle
• Structure
• Ubiquinone-10