Paramagnetic isoprenoid carrier lipids. 1. Chemical synthesis and incorporation into model membranes

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Abstract
The synthesis, purification and characterization of 2 types of spin-labeled glycosyl carrier lipids and shorter chain isoprenols are described. As models for phosphorylated lipid intermediates, phosphodiesters of tempol and the prenols dolichol, ficaprenol, solanesol, phytol and farnesol were prepared. For analogues of neutral species, each prenol was esterified with a pyrrolidinecarboxylic acid based label. Triprophylbenzenesulfonyl chloride was used as the condensing agent in both cases. Phosphodiester yields ranged from 36% for the 55-carbon compound to > 66% for the 95-carbon prenol. Both types of probes were incorporated into phospholipid bilayers, where each became oriented with the artificial head group at, or very close to, the water-hydrocarbon interface. ESR spectra of the phosphodiesters are matrix dependent, indicating rapid isotropic tumbling in chloroform but highly anisotropic reorientation in unsaturated phosphatidylcholine (PC) hosts. Rotation or large amplitude oscillation about either or both the tempo C4-O linkage and the P.sbd.O (chain) bond as well as whole molecule rotation within the bilayer could account for the observed .chi.-axis anisotropy. Segmental motion within the polyprene chain does not appear to be a determinant.