Phosphatidylcholine species

This is a respectable type of separation, and yet it is obvious that not all compounds or classes of compounds are separated precisely and neatly from each. There simply is not such a magic system, and one must realize that further fractionation may be necessary. It is interesting to note that phosphatidylcholine and sphingomyelin tend to blend together. Usually the more unsaturated phosphatidylcholine species elute early on, followed by the more saturated one. By judicious handling of solvent eluate volume (by a fraction collector), a quite reasonable separation can be obtained. 

Although the majority of laboratories use a commercially availabie method for L/S determination (Fetal-Tek, Helena Laboratories, Beaumont, Tex.), some continue to use methods developed in their own laboratories (the so-called "home brew methods). Because there are many techniques, laboratories should be very careful when establishing medical decision limits. Some methods measure all phosphatidylcholine species, both saturated and unsaturated. Different staining methods will differentially stain phos-phatidylchohne compared with the biological internal stan-... 

Parks JS, Thuren TY, Schmitt JD. Inhibition of lecithin cholesterol acyltransferase activity by synthetic phosphatidylcholine species containing eicosapentaenoic acid or docosahexaenoic acid in the sn-2 position. J Lipid Res 1992 33 879-887. 

Fig. 7. Oxidation of LDL phospholipids in the generation of minimally modified LDL. Seeding molecules like HPETE, HPODE, and cholesteryl linoleate hydroperoxide (CE-OOH) are proposed to trigger the oxidation of l-palmitoyl-2-arachidonoyl phosphatidylcholine in LDL, leading to the generation of three oxidized phosphatidylcholine species that confer atherogenic activity to minimally modified LDL. 12-LO, 12-lipoxygenase. Adapted from Ref. [28]. Reproduced with permission from the publisher.

Simoes, A. P., Fiebig, S., Wunderlich, F., Vial, H., Roelofsen, B. and Op den Kamp, J. A. F. (1993) Plasmodium chabaudi-parashized erythrocytes phosphatidylcholine species of parasites and host cell membranes. Mol. Biochem. Parasitol. 57 345-348. 

Lipid composition of ChS and ChR cells. ChS and ChR cells, respectively cultivated at 26 C on their standard medium exhibited slight differences in their lipid composition and content (table 1). Even the molecular phosphatidylcholine species showed the same composition and distribution in both cell lines. 

Table 3.7 The fatty acid composition of cholesteryl esters, phosphatidylcholine and phosphatidylethanolamine in the milks of some species... 

A Cantafora, R Masella. Improved determination of individual molecular species of phosphatidylcholine in biological samples by high performance liquid chromatography with internal standards. J Chromatogr 593 139-146, 1992. 

BJ McKeone, K Osmundsen, D Brauchi, Q Pao, C Payton-Ross, C Kilinc, FA Kummerow, HJ Pow-nall. Alterations in serum phosphatidylcholine fatty acyl species by eicosapentaenoic and docosa-hexaenoic ethyl esters in patients with severe hypertriglyceridemia. J Lipid Res 38 429-436, 1997. 

RL Glass. Semipreparative high performance liquid chromatographic separation of phosphatidylcholine molecular species from soybean leaves. J Liq Chrom 14 339 -349, 1991. 

P Therond, M Couturier, JF Demelier, F Lemonnier. Simultaneous determination of the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their corresponding hydroperoxides obtained by lipoxygenase treatment. Lipids 28 245-249, 1993. 

The pathway for the synthesis of dipalmitoyl-phos-phatidylcholine is illustrated in figure 19.5. The starting species of phosphatidylcholine is made by the CDP-choline pathway (see fig. 19.4). The fatty acid at the sn-2 position, which is usually unsaturated, is hydrolyzed by phospholi-pase A2, and the lysophosphatidylcholine is reacylated with palmitoyl-CoA. This modification permits alteration of the properties of the phospholipid without resynthesis of the entire molecule, a strategy called remodeling. Deacylation-reacylation of phosphatidylcholine occurs in other tissues and provides an important route for alteration of the fatty acid substituents at both the sn-1 and sn-2 positions. For example, fatty acids at the sn-2 position can be replaced by arachidonic acid, which is stored there until needed for eicosanoid biosynthesis, as we discuss later in this chapter. 

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