Synthesis of Hybrid Lipid Probes:  Derivatives of Phosphatidylethanolamine-Extended Phosphatidylinositol 4,5-Bisphosphate (Pea-PIP₂)

The total asymmetric synthesis of a novel hybrid lipid possessing a 2,3-diacylthreitol backbone, rather than a 1,2-diacylglycerol backbone, is described. The title compound, Pea-PIP(2), possesses a phosphatidylethanolamine (PE) headgroup at the 1-position and a phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P(2)) headgroup at the 4-position. Reporters (biotin, fluorophores, spin label) were covalently attached to the free amino group of the PE, such that these reporters were targeted to the lipid-water interface. The diacyl moieties allow incorporation of Pea-PIP(2) into a lipid bilayer, while the PtdIns(4,5)P(2) moiety in the aqueous layer was specifically recognized by PtdIns(4,5)P(2)-specific binding proteins.