Interaction of lutein with phosphatidylcholine bilayers

The interaction of lutein, an inhibitory uncoupler of mitochondrial oxidative phosphorylation, with phospholipid bilayers has been examined employing a variety of physical methods. Differential calorimetric scans revealed that incorporation of lutein into aqueous dispersions of dipalmitoylphosphatidylcholine broadened the main transition endotherm and decreased the transition enthalpy as well as the size of the cooperative unit without change in the temperature of transition. Permeability of the bilayer to ascorbate was enhanced significantly by the presence of lutein. The trapped volume of the vesicles was decreased. Incorporation of lutein broadened the NMR peaks of both the acyl side-chain methylene and terminal methyl protons without and change in the line-width of the choline head-group methyl proton signal. This indicated the ability of the compound to integrate deep into the hydrophobic regions of the phospholipids bilayer distal to the polar regions. These results suppor our earlier biochemical studies which revealed that the deleterious action of lutein on mitochondrial oxidative phosporylation could be due to its stability to interact with membrane components and perturb the structure.