The interaction of ubiquinone-3 with phospholipid membranes

The effects of ubiquinone-3 (UQ) on dipalmitoylphosphatidylcholine (DPPC) membrane were studied by surface monolayer, differential scanning calorimetry (DSC) and fluorescence techniques. DPPC and UQ are proved to be freely miscible in the mixed monolayer at an air/water interface, and to be partially miscible in bulk phase, i.e. bilayer and solid phase. There is a condensing interaction between UQ and DPPC in the UQ/DPPC mixed monolayers, The solubility of UQ in the DPPC is about 20 mole% and the solubility of DPPC in UQ is about 10 mole%, The membrane fluidity of DPPC was increased by the addition of UQ and the phase transition temperature was decreased. (C) 1999 Federation of European Biochemical Societies.