Time-resolved fluorescence and differential scanning calorimetry were used to determine the partitioning of coumarin 152 (C152) into large unilamellar vesicles composed of binary mixtures of two phosphatidylcholines (12:0/12:0 DLPC and 14:0/14:0 DMPC) and vesicles composed of binary mixtures of a phosphatidylcholine and a phosphatidylethanolamine (14:0/14:0 DMPC and 14:0/14:0 DMPE). Time-resolved fluorescence indicated that C152 partitioning into DLPC/DMPC mixtures showed nearly ideal behavior that was described with weighted contributions from C152 partitioning into pure DLPC and pure DMPC vesicles. In contrast, C152 partitioning into DMPC/DMPE mixtures was distinctly non-ideal. For DMPC/DMPE lipid vesicles having DMPC mole fractions between 10-80%, C152 partitioning into the bilayer was measurably enhanced near the melting temperature, relative to expectations based simply on weighted contributions from C152 partitioning into vesicles comprised of pure lipids. For vesicles comprised of pure DMPE, C152 shows almost no partitioning into the membrane with ≥80% of the solute remaining in the buffer solution at temperatures between 10-50 C. These findings will be presented in the context of solute accumulation in biological membranes and its impact on solute persistence in environmental systems.

Solute partitioning and solvation in lipid membranes: Microscopic origins of bioaccumulation

2019 Spring National Meeting

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