Sugar surfactant-based solutions as host systems for enzyme activity measurements

We used fluorogenic substrates, namely, alkyldiacyl glycerols labeled with a fluorophore and a fluorescence quencher, to measure lipase activities. Fo r this optical lipase assay it is necessary that the water-insoluble fluoro genic substrates are dispersed in an aqueous medium in the presence of appr opriate detergents in order to obtain well-defined and reproducible systems with high optical transparency. The activity of lipases critically depends on the supramolecular organization of the substrate. Therefore, we tested different solutions containing nonionic surfactants and organic phases for their potential use as host systems for fluorogenic lipids. We then determi ned the pseudoternary phase diagram for the system buffer-alkyl polyglucosi de-hexanol, which showed the highest apparent enzyme activities, in the buf fer corner. We performed structural investigations on micellar sugar surfac tant solutions within the L-1 phase with and without hexanol using small-an gle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and dyn amic light scattering (DLS) in order to investigate a possible correlation between Lipase activity and the structure of the aggregates present in the host system.