Partition of parinaroyl phospholipids in mixed head group systems

Partitioning of 1-palmitoyl-2-cis-parinaroylphosphatidylcholine, 1-palmitoyl-2-cis-parinaroylphosphatidylethanolamine, 1-oleoyl-2-trans-parinaroylphosphatidylcholine, and 1-oleoyl-2-trans-parinaroylphosphatidylethanolamine between solid-phase phosphatidyelthanolamine and between solid-phase phosphatidylcholine and fluid-phase phosphatidylethanolamine is investigated. The partitioning of these probes is shown to be nearly independent of their head group. Fluorescence polarization of the above probes plus trans-parinaric acid, cis-parinaric acid, 1-palmitoyl-2-trans-parinaroylphosphatidylcholine, 1-oleoyl-2-cis-parinaroylphosphatidylcholine, and 1-oleoyl-2-cis-parinoylphosphatidylethanolamine is examined in phospholipids isolated from LM cell (mouse fibroblast) plasma membranes. A fraction of these phospholipids undergoes a gel-liquid-crystalline phase transition beginning near the physiological temperature. The parinaroyl probes with the highest solid-fluid-phase partition coefficients [Welti, R., & Silbert, D. F. (1982) Biochemistry (preceding paper in this issue)] detect the transition most readily. The degree of response to this transition also appears to depend on the acyl chains of the parinaroyl phospholipid rather than the probe head group. This is further demonstrated with the phosphatidylcholine and phosphatidylethanolamine fractions from LM cell plasma membranes.