1-PALMITOYL-2-[3-(DIPHENYLHEXATRIENYL) PROPANOYL]-SN-GLYCERO-3-PHOSPHOETHANOLAMINE AS A FLUORESCENT MEMBRANE PROBE - SYNTHESIS AND PARTITIONING PROPERTIES

We have synthesized the fluorophore 1-palmitoyl-2-[3-(diphenylhexatrienyl) propanoyl]-sn-glycero-3-phosphoethanolamine, a fluorescent phospholipid which has a polar phosphatidylethanolamine head group, but one of the two chains is replaced by a diphenylhexatriene moiety. The partitioning of this probe, between gel-phase and liquid crystalline-phase of multilamellar vesicles of binary composition (either PC-PC or PC-PE mixtures) was measured and systematically compared to that of the choline analogue DPHpPC (R.A. Parente and B.R. Lentz (1985) Biochemistry 24, 6178-6185). We found in PC mixtures that DPHpPE partitions preferentially in the gel-phase of the vesicles (Kf/s = 0.8), contrary to the choline analogue which partitions preferentially in the fluid-phase. In heterogeneous PC-PE mixtures, DPHpPE never shows preferential partitioning for a PE-rich phase (Kf/s = 1.35 for DEPC/DPPE vesicles: Kf/s = 0.5 for LoPE/DPPC vesicles). These partitioning data are compared to previous results in the literature and tentative explanations are given. In conclusion, this new molecule cannot be used as a specific probe for membrane domains rich in phosphatidylethanolamine. © 1990.