The micellar properties of mixtures of GM1 ganglioside and the non-ionic amphiphile Triton X-100 in 25 mM Na phosphate-5 mM di Na EDTA buffer (pH = 7.0) were investigated by quasielastic light scattering in a wide range of Triton/GM1 molar ratios and in the temperature range 15-37°C. These measurements: (a) provided evidence for the formation of mixed micelles; (b) allowed the determination of such parameters as the molecular weight and the hydrodynamic radius of the mixed micelles; (c) showed the occurrence of statistical aggregates of micelles with increasing temperature and micelle concentration. Galactose oxidase was chosen for studying the relation between enzyme activity and micellar properties. The action of the enzyme on GM1 was found to be strongly dependent on the micellar structure. In particular: (a) galactose oxidase acted very poorly on homogeneous GM1 micelles, while affecting mixed GM1/Triton X-100 micelles; (b) at fixed GM1 concentration the oxidation rate increased by enhancing Triton X-100 concentration and followed a biphasic kinetics with a break at a certain Triton X-100 concentration; (c) the formation of statistical micelle aggregates was followed by inhibition of the enzyme activity.
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