Partition of parinaroyl phospholipid probes between solid and fluid phosphatidylcholine phases

The partitioning of parinaroyl phospholipid probes between solid- and fluid-phase phospholipid is examined. The immiscible model system dipalmitoylphosphatidylcholine and palmitoyldocosahexaenoylphosphatidylcholine is used. Fluorescence quantum yields and fluorescence polarization are used to calculate Kps/f, the solid to fluid phase partition coefficient of each probe [Sklar, L. A., Miljanich, G. P. & Dratz, E. A. (1979) Biochemistry 18, 1707-1716]. Like free trans-parinaric acid (9,11,13,15-all-trans-octadecatetraenoic acid) 1-palmitoyl-2-trans-parinaroylphosphatidylcholine and 1-palmitoyl-2-tra-parinaroylphosphatidylethanolamine partition strongly into solid phase with mean Kps/fs of 7 +/- 4 and 9 +/- 5, respectively. Like free cis-parinaric acid (9,11,13,15-cis-trans,trans,cis-octadecatetraenoic acid), another group of phospholipid probes prefer fluid phase just slightly or partition equally between fluid and solid phases. The Kps/f of 1-palmitoyl-2-cis-parinaroylphosphatidylcholine is 0.6 +/- 0.2, that of 1-palmitoyl-2-cis-parinaroylphosphatidylethanolamine is 1.0 +/- 0.3, that of 1-oleoyl-2-trans-parinaroylphosphatidylcholine is 0.6 +/- 0.3, and that of 1-oleoyl-2-trans-parinaroylphosphatidylethanolamine is 0.7 +/- 0.3. Two probes partition more strongly into fluid-phase phospholipid. These are 1-oleoyl-2-cis-parinaroylphosphatidylcholine with a Kps/f of 0.2 +/- 0.1 and 1-oleoyl-2-cis-parinaroylphosphatidylethanolamine with a Kps/f of 0.4 +/- 0.4.