Partition of parinaroylphosphatidylethanolamines and parinaroylphosphatidylglycerols in immiscible phospholipid mixtures.

Partitioning of two parinaroyl phosphatidylethanolamines and two parinaroyl phosphatidylglycerols between solid and fluid phase phospholipids was examined. Fluorescence quantum yields and fluorescence polarization measurements were used to calculate Ks/fp, the solid to fluid partition coefficient of each probe (Sklar, L.A., Miljanich, G.P. and Dratz, E.A. (1979) Biochemistry 18, 1707-1716). In the immiscible mixture dipalmitoylphosphatidylcholine and dilinoleylphosphatidylcholine, both 1-palmitoyl-2-trans-parinaroylphosphatidylethanolamine and 1-palmitoyl-2-transparinaroylphosphatidylglycerol partitioned preferentially into solid phase lipid with mean Ks/fp values (calculated from quantum yields) of 3.4 +/- 1.5 and 2.1 +/- 0.7, respectively. In contrast, 1-oleoyl-2-cis-parinaroylphosphatidylethanolamine and 1-oleoyl-2-cis-parinaroylphosphatidylglycerol partitioned preferentially into fluid phase lipid in the same model system with mean Ks/fp values (calculated from quantum yields) of 0.44 +/- 0.26 and 0.16 +/- 0.07, respectively. Fluorescence polarization data on the same four parinaroyl phospholipids in mixtures of solid-phase dimyristoylphosphatidyl ethanolamine and fluid-phase dilinoleoylphosphatidylglycerol were similar to those obtained in the immiscible phosphatidylcholine system, demonstrating that the partitioning of these probes is not strongly dependent on head group. Knowledge of the partition properties of these fluorescent probes is relevant to use of these probes in investigation of the phase behavior of Escherichia coli inner membrane lipids, since phosphatidylethanolamine and phosphatidylglycerol species account for approximately 95% of these lipids.