Ether linked lipids

Different membrane lipids (ether linked in Archaea, phospho-ester linked in bacteria)... 

Some animal tissues and some unicellular organisms are rich in ether lipids, in which one of the two acyl chains is attached to glycerol in ether, rather than ester, linkage. The ether-linked chain may be saturated, as in the alkyl ether lipids, or may contain a double bond between C-l and C-2, as in plasmalogens (Fig. 10-9). Vertebrate heart tissue is uniquely enriched in ether lipids about half of the heart phospholipids are plasmalogens. The membranes of halophilic bacteria, ciliated protists, and certain invertebrates also contain high proportions of... 

FIGURE 10-9 Ether lipids. Plasmalogens have an ether-linked alkenyl chain where most glycerophospholipids have an ester-linked fatty acid (compare Fig. 10-8). Platelet-activating factor has a long ether-linked alkyl chain at C-l of glycerol, blit C-2 is ester-linked to acetic acid,... 

Most cells continually degrade and replace their membrane lipids. For each hydrolyzable bond in a glycerophospholipid, there is a specific hydrolytic enzyme in the lysosome (Fig. 10-15). Phospholipases of the A type remove one of the two fatty acids, producing a lysophospholipid. (These esterases do not attack the ether link of plasmalogens.) Lysophospholipases remove the remaining fatty acid. 

Inclusion of other molecules of irregular shape within membranes also lowers Tm. However, a molecule of cholesterol can pack into a bilayer with a cross-sectional area of 0.39 nm2, just equal to that of two hydrocarbon chains.49 It tends to harden membranes above Tm but increases mobility of hydrocarbon chains below Tm.97 -100 A complex of cholesterol and phosphatidylcholine may form a separate phase within the membrane.101102 The ether-linked plasmalogens may account for over 30% of the phosphoglycerides of the white matter of the brain and of heart and ether linked phospholipids are the major lipids of many anaerobic bacteria.103 Their Tm values are a few degrees higher than those of the corresponding acyl phospholipids.104... 

Ether-linked lipids constitute up to 35% of the total phospholipid in molluscs. Although they are usually regarded as animal constituents, small amounts of ether-linked lipids have been identified in plants. The major phospholipids of archaebacterial membranes are ether-linked derivatives of the polyprenyl phytanyl group and of the dimeric biphytanyl group (Chapter... 

C40 Phytoene Carotenes Archaeobacterial ether-linked lipids... 

The linker group that bridges the cationic lipid headgroup with the hydrocarbon moiety controls the biodegradability of a cationic amphiphile. Most of the linker bonds are ether, ester, or amide bonds (Fig. 1). Compounds with ether links generally render better transfection efficiency. However, they are more stable and may cause higher toxicity, while cationic lipids with ester links such as DOTAP are more biodegradable and less cytotoxic in cultured cells [28, 39]. Noteworthy,... 

Fig. 8 Transfection of HeLa cells using cholesterol-based ether linked cationic lipids with different headgroups at N/P ratio 3 1, in the presence of 10% serum the formulations were optimized for the helper lipid DOPE content [38]...

As mentioned in Chapter 2, the alkylacylcholine phosphoglycerides predominate in the choline-containing fraction in the majority of mammalian cells. On the other hand, the alkenylacyl form predominates in the ethanolamine-containing fraction. It is important to stress that these ether-linked lipids are found essentially only in the choline- and ethanolamine-containing phospho-glyceride. The reason for this high specificity of distribution is not known at present. 

Debuch, H. and Seng, P. (1972) The history of ether-linked lipids through 1960, in Ether Lipids Chemistry and Biology, F. Snyder, editor, Academic Press, New York, pp. 1-24. 

Blank, M.L., Cress, E.A., Smith, Z.L., Snyder, F. 1991. Dietary supplementation with ether-linked lipids and tissue lipid composition. Lipids. 26, 166-169. 

Membrane lipids. Linkage to glycerol ester-linked ether-linked ester-linked... 

The Halobacteriaceae, commonly referred to as the halobacteria, are a family of extremely halophilic archaebacteria [113]. As in other archaebacteria, their membranes contain ether-linked lipids. The primary lipids present are diphytanyl phospholipids [113]. Their cell walls are also unique in structure and lack muramic acid. There are several species of halobacteria that vary considerably in their physiological characteristics. The halobacteria are unicellular rods or cocci. More recently flat, square and box-shaped cells have been described. Halobacteria are found growing in salterns or natural salt lakes and on the surface of salted fish. They often form dense planktonic blooms and can form massive accumulations on solid substrates. They may be involved in mat communities in hypersaline environments. 

Synder F. Ether-linked lipids and their bioactive species occurrence, chemistry, metabolism, regulation and function. In Biochemistry of Lipids and Lipoproteins and Membranes. Vance DE and Vance JE, eds. 1996. Elsevier, Amsterdam, pp. 183-210... 

Dembitsky VM. Betaine ether-linked glycerolipids chemistry and biology. Prog. Lipid Res. 1996 35 1-51. 

PAF is an ether linked pho hoglyceiide. Giemical stmctuie of this lipid mediator was determined to be l-O-alkyl-2-acetyl-sn-glycero-3-phosphorylcholine (Fig. 1). In literature PAF has also been termed as PAF-acether, and AGEPC (alkyl acetyl glycero ether phosphoryl Moline). Excellent reviews have documented these historical developments (Hanahan, 1986, Snyder, 1985). In this... 

Kates M (1978) The phytanyl ether-linked polar lipids and isoprenoid neutral lipids of... 

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