Lipids galactolipids

DORMANN, P., BALBO, I., BENNING, C., Arabidopsis galactolipid biosynthesis and lipid trafficking mediated by DGD1, Science, 1999, 284,2181-2184. 

The membrane lipids, in particular phospholipids and galactolipids, make up the predominant fraction of lipids in potato tubers, and only trace amounts of triacylglycerols are present. For example, in the tuber of cultivar Desiree, the membrane lipids constitute 92.8 mol-% of total lipids, whereas triacylglycerol amounts to only 1.1 mol-% (Klaus et al., 2004). 

A newer approach for lipid analysis is electrospray ionization tandem mass spectrometry (ESI-MS/MS) (Welti et al., 2002). This method requires limited sample preparation and sample size to identify and quantify lipids. Fauconnier et al. (2003) used ESI-MS/MS to analyze phospholipid and galactolipid levels during aging of potato tubers. 

The second group of membrane lipids are those that predominate in plant cells the galactolipids, in which one or two galactose residues are connected by a gly-cosidic linkage to C-3 of a 1,2-diacylglycerol (Fig. 10-10 see also Fig. 10-6). Galactolipids are localized in the thylakoid membranes (internal membranes) of chloroplasts they make up 70% to 80% of the total membrane lipids of a vascular plant. They are probably the most... 

Diacylglycerols can also be converted to a variety of glycolipids such as the galactolipids of chloro-plasts (Eq. 21-8). See also Chapter 8. These are the major lipids of photosynthetic membranes.98153-155 Some bacteria, e.g., the mycoplasma Acholeplasma... 

HPLC of galactolipids from a membrane treated with galactose oxidase. The membrane treated with galactose oxidase is extracted with chloroform/methanol as described above. The extract containing up to 1 mg of total lipids is shaken with a solution of 2 mg of dinitrophenylhydrazine HC1 in 100 pi pyridine for 2 h at room temperature. The solvent is evaporated to dryness under a... 

Myelin galactolipid analysis by HPLC. Fig. 2 and 3 show HPLC chromatograms obtained from myelin lipids on Silica column and reverse phase column, respectively. Reverse phase HPLC of mono-galactosyl diglyceride and its 1-0-alkyl ether homolog was not examined but typical chromatograms of these lipids obtained from calf brain stem were presented previously (11 ). Myelin was obtained from 25 day-old rat brains. 

Lysophosphatidylcholine makes up about 70% of the lipids present in oat starch.11 For AC Hill oat starch, free fatty acids dominated the neutral lipids (NL), lysophosphatidylcholine (a phospholipid, PL) and digalactosyldiglyceride (a galactolipid, GL).20 The predominant fatty acid was C18 2 in NL and C16 0 in PL and GL. Most of the phosphorus present in oat starch is present in lipids.8 There is a significant... 

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... 

Other abundant lipids in myelin are galactosylcerebrosides (Gal-C) and their sulfated derivatives (sulfatides). GalC represent 20% lipid dry weight in mature myelin. Immunological and chemical perturbation studies indicate that these lipids are involved in oligodendrocyte differentiation, myelin formation and myelin stability. These galactolipid-deficient animals exhibit severe tremor, hindlimb paralysis and display electro-physiological deficits in both CNS and PNS (Baumann and Pham-Dinh, 2001). 

The galactolipids are known to be distributed asymmetrically in the lipid bilayer - about 60% of the galactoUpids are present in the outer leaflets and 40% in the inner leaflets of the thylakoid-membrane bilayer. The strong interaction between the head-groups of the galactolipid molecules determine then-packing properties and enhance the stability of the membrane. Formation of the bilayer structure of the thylakoid membrane also depends on the presence of proteins. Another characteristic of the thylakoid lipids is their high content ofthe trienoic acid, (C18 3) a-linolenic acid, which contributes to the fluidity of the membrane, necessary for the diffusion of lipophilic compounds such as plastoquinone, and the lateral diffusion of protein complexes. 

We now look at a recent model for the structure of the antenna complex and its relationship to the reaction center in the cytoplasmic membrane, as shown in some detail in Fig. 2. The size of chlorosomes ranges from 50 to 100 nm in width and -100 to 300 nm in length. The outer layer, or envelope, of the chlorosome is a galactolipid monolayer in which polypeptides of 18- and 11 -kDa molecular mass are embedded. Inside the lipid envelope are rodlike structures, the so-called rod elements, as previously noted, each of which is about 5-10 nm in diameter and run nearly the full length of the chlorosome. The rod elements were previously thought to contain BChl c-protein complexes, but recent studies have shown that the BChl c molecules are present simply as self-aggregated oligomers. 

---