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Temperature-Dependent Partitioning of C152 in Binary Phosphatidylcholine Membranes and Mixed Phosphatidylcholine/Phosphatidylethanolamine Membranes
journal contribution
posted on 2017-07-20, 00:00 authored by Christine
A. Gobrogge, Victoria A. Kong, Robert A. WalkerTime-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). Differential scanning calorimetry showed
that both DLPC/DMPC and DMPC/DMPE are miscible in lipid vesicles.
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 nonideal. For DMPC/DMPE lipid vesicles having DMPC mole
fractions between 10 and 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. The origin of this behavior remains
uncertain. 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 and 50
°C.