DISATURATED AND DIPOLYUNSATURATED PHOSPHOLIPIDS IN THE BOVINE RETINAL ROD OUTER SEGMENT DISK MEMBRANE

TLC was used to separate the major phospholipid headgroup classes of the rod outer segment disc membrane into subfractions which differ markedly in fatty acid composition. At least 18% of the rod outer segment phosphatidylcholine must contain 2 saturated fatty acids. Furthermore, 2 unsaturated fatty acids are found in at least 43% of the phosphatidylserine, 24% of the phosphatidylcholine and 24% of the phosphatidylethanolamine. The unsaturated acids are predominantly polyunsaturated in all cases. A similar separation, but with less resolution, was achieved with silicic acid column chromatography. The temperature dependence of the polarization of fluorescence of trans-parinaric acid (9,11,13,15-all-trans-octadecatetraenoic acid) showed that the thermal behavior of aqueous dispersions of the phosphatidylcholine subfractions was consistent with their fatty acid compositions.