Determination of the critical micelle concentration of short-chain ubiquinones in model systems

We have investigated the critical micelle concentrations of short-chain ubiquinone and ubiquinol homologs in water, aqueous buffers and ethanol-water mixtures. The physical state of ubiquinones becomes nonmonomeric at definite concentration that can be identified because the aggregation is accompanied by a red shift of λmax and a decrease of the extinction coefficient. Systematic studies following the transition dipole moment against quinone concentration have established that the critical micelle concentration is a function of isoprenoid chain length and state of oxidation of the quinones and of the dielectric constant and ionic strength of the medium. The thermodynamics of micelle formation point out that the quinone ring has a strong tendency to be located in a hydrophobic environment