Lipids sulfolipid

Glycolipids are important constituents of the plasma membranes, of the endoplasmic reticulum, and of chloroplasts. The cerebrosides and their sulfate esters, the sulfatides, are especially abundant in myelin. In plant membranes, the predominant lipids are the galactosyl diglycerides.29 74 The previously described ether phospholipids (archaebacteria), ceramide arnino-ethylphosphonate (invertebrates), and sulfolipid (chloroplasts) are also important membrane components. 

Whether polymerized model membrane systems are too rigid for showing a phase transition strongly depends on the type of polymerizable lipid used for the preparation of the membrane. Especially in the case of diacetylenic lipids a loss of phase transi tion can be expected due to the formation of the rigid fully conjugated polymer backbone 20) (Scheme 1). This assumption is confirmed by DSC measurements with the diacetylenic sulfolipid (22). Figure 25 illustrates the phase transition behavior of (22) as a function of the polymerization time. The pure monomeric liposomes show a transition temperature of 53 °C, where they turn from the gel state into the liquid-crystalline state 24). During polymerization a decrease in phase transition enthalpy indicates a restricted mobility of the polymerized hydrocarbon core. Moreover, the phase transition eventually disappears after complete polymerization of the monomer 24). 

As an example of an asymmetric membrane integrated protein, the ATP synthetase complex (ATPase from Rhodospirillum Rubrum) was incorporated in liposomes of the polymerizable sulfolipid (22)24). The protein consists of a hydrophobic membrane integrated part (F0) and a water soluble moiety (Ft) carrying the catalytic site of the enzyme. The isolated ATP synthetase complex is almost completely inactive. Activity is substantially increased in the presence of a variety of amphiphiles, such as natural phospholipids and detergents. The presence of a bilayer structure is not a necessary condition for enhanced activity. Using soybean lecithin or diacetylenic sulfolipid (22) the maximal enzymatic activity is obtained at 500 lipid molecules/enzyme molecule. With soybean lecithin, the ATPase activity is increased 8-fold compared to a 5-fold increase in the presence of (22). There is a remarkable difference in ATPase activity depending on the liposome preparation technique (Fig. 41). If ATPase is incorporated in-... 

In addition to enzymatic hydrolysis of natural lipids in polymeric membranes as discussed in chapter 4.2.2., other methods have been applied to trigger the release of vesicle-entrapped compounds as depicted in Fig. 37. Based on the investigations of phase-separated and only partially polymerized mixed liposomes 101, methods to uncork polymeric vesicles have been developed. One specific approach makes use of cleavable lipids such as the cystine derivative (63). From this fluorocarbon lipid mixed liposomes with the polymerizable dienoic acid-containing sulfolipid (58) were prepared in a molar ratio of 1 9 101115>. After polymerization of the matrix forming sulfolipids, stable spherically shaped vesicles are obtained as demonstrated in Fig. 54 by scanning electron microscopy 114>. 

Table III gives the results of an experiment in which the effect of serum manipulation on sulfolipid synthesis by dissociated brain cells was examined. The cells isolated from the embryonic mouse brain were grown on the medium containing calf serum (20%) for 3 days by which time most of the cells would have attached to the substratum. On the 4th day, the medium was replaced by fresh medium containing calf serum, calf serum + 13(2 x 10 8m), hypothyroid calf serum, or hypothyroid calf serum + 13(13 ng/ml). Cultures were grown for another week and then labeled with 400 pCi for 16 h. The lipids...

SPHINGOLIPIDS AND OTHER LIPIDS Phytosphingolipids Cerebroside Phytosphingosine Sulfolipids... 

The thylakoid membranes contain the energy-transducing machinery light-harvesting proteins, reaction centers, electron-transport chains, and ATP synthase. They have nearly equal amounts of lipids and proteins. The lipid composition is highly distinctive about 40% of the total lipids are galactolipids and 4% are sulfolipids, whereas only 10% are... 

Sulfolipids Free fatty acids Lipid-soluble vitamins Pigments Phenolic compounds Metals and Metalloproteins... 

Farooqui, A. A., Metabolism of sulfolipid in mammalian tissues. Adv. Lipid Res. 18, 159-202... 

CGT) and cerebroside sulfotransferase (CST) neuronal lipid storage was provoked. CGT-transgenic ASA(—/—) [CGT/ASA(—/—)] mice showed an accumulation of Cl8 0 fatty acid-containing sulfogalactosylceramide in the brain. Histochemicaly, an increase in sulfolipid storage could be detected in central and peripheral neurons of both CGT/ASA(—/—) and CST/ASA(—/—) mice compared with ASA(—/—) mice. CGT/ASA(—/—) mice developed severe neuromotor coordination deficits and weakness of hindlimbs and forelimbs. 

Direct evidence for degradation of lipids can be obtained by prelabeling the thylakoid sulfolipid of, e.g., microalgae with Sg-sulfate. When oxyfluorfen or norflurazon were applied to cause a 90% decrease of a- and p-carotene over 2 culture days, more than 90% of the radioactivity of the sulfolipid disappeared in the oxyfluorfen sample. Using norflurazon, only 20% of the sulfolipid was degraded during this period ( ),... 

Farooqui, A.A. (1981). Metabolism of Sulfolipids in Mammalian Tissues . Advances in Lipid Research, 18, 159-202. 

The photosynthetic membranes of higher plant chloroplasts have an unusual lipid composition 60 - 80 % galactolipids (MGDG, DGDG), approx. 10 % sulfolipid (SQDG), approx. 10 % (trans 16 3) phosphatidyl-glycerol (PG), 5 - 10 % phosphatidylcholines (PC) and hardly or no... 

Although most attention has been directed toward the analysis of leaves or storage tissues, data are available for other plant tissues such as roots and shoots. In general, the high linolenic acid content of leaves is replaced by linoleic acid in roots. In addition, phosphatidylcholine becomes relatively more abundant as the contribution toward total acyl lipids made by the chloroplastic galactosylglycerolipids, sulfolipid, and phosphatidylglyc-erol declines. A few representative papers are those by Body (1974), Cher-rad et al. (1974), Jarvis and Duncan (1974), and Sukhija et al., (1976). 

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