Di(polyprenyl) Phosphates as Models for Primitive Membrane Constituents: Synthesis and Phase Properties

Identical- and mixed-chain di(polyprenyl) phosphates, derived from 3-methyl-2-buten-1-ol, (E)-geraniol, (E,E)-farnesol, (E,E,E)-geranylgeraniol, (R)-citronellol, or (R)-tetrahydrogeraniol have been synthesized by phosphitylation and oxidation with iodine/water. These phosphates gave organized systems in water, in particular vesicles, the physical properties of which were studied by photon correlation spectroscopy, electron microscopy, entrapment of a fluorescent dye (calcein), 31P NMR, stopped-flow/light-scattering studies, and fluorescence polarization with lipophilic probes. Interdigitation of mixed-length phosphates was not found to have any favorable effect on the stability of the vesicles. The C>15 vesicles were formed despite the fact that they are composed of only one molecular species and are devoid of any reinforcer, but those with two geranyl chains appeared to be rather fragile. Phosphates containing C5 chains are soluble in water. The results obtained lend weight to the hypothesis that polyprenyl phosphates might have been primitive membrane constituents, and stimulate the search for appropriate reinforcers.