Lipids diglycerides

TLC spots with marker reveal the presence of free fatty acids (FFA), diglyceride (DG), monoglyceride (MG) but negligible amount of TG. GCMS of fatty acid— methyl esters (FAME) from lion mane presented evidence for fatty acids ranging from C9-C24 (Figs. 5.3- 5.6). Low volatility molecules like nonanedioic acid (Fig. 5.3), tridecanoic acid (Fig. 5.4), 12-methyl tridecanoic acid were also present in lion hair lipids. In addition fatty acids such as myristic, pentadecanoic, palmitic, heptanoic, stearic and octadecenoic acids (Fig. 5.5) have also been detected. Erucic... 

Seeds of the violet, Viola odorata are disseminated by the ant Aphaenogaster rudis. Elaiosomes (appendages attached to the outside of the seed coat) often contain high concentrations of lipids and are associated with attraction of the ants. 1,2-Diolein, a diglyceride, is largely responsible for this attraction (124). 

Low-molecular-weight surfactants ( emulsifiers ) are important ingredients in food products. The types of surfactants most commonly studied in food colloids research are phospholipids (lecithin), mono/diglycerides (particularly glycerol monostearate), polysorbates (Tweens), sorbitan monostearate or monooleate (Spans), and sucrose esters. These small lipid-based amphiphiles can typically lower the interfacial tension to a greater extent than the macromolecular amphiphiles such as proteins and certain gums (Bos and van Vliet, 2001). 

Increased synthesis of lipid or uptake. Increased synthesis of lipid may be the cause of fatty liver after hydrazine administration as this compound increases the activity of the enzyme involved in the synthesis of diglycerides. Hydrazine also depletes ATP and, however, inhibits protein synthesis. Large doses of ethanol will cause fatty liver in humans, and it is believed that this is partly due to an increase in fatty acid synthesis. This is a result of an increase in the NADH/NAD"1" ratio and therefore of the synthesis of triglycerides. Changes in the mobilization of lipids in tissues followed by uptake into the liver can also be another cause of steatosis. 

The lipids of milk are composed of about 98% triglycerides, with much smaller amounts of free fatty acids, mono-and diglycerides, phospholipids, sterols, and hydrocarbons. Chapter 4 deals in detail with the composition of milk lipids. 

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. 

Emulsifiers. The chemical structures of emulsifiers, or surfactants, enable these materials to reduce the surface tension at the interface of two immiscible surfaces, thus allowing the surfaces to mix and form an emulsion. An emulsifier consists of a polar group, which is attracted to aqueous substances, and a hydrocarbon chain, which is attracted to lipids. Emulsifiers include mono- and diglycerides, lecithin, propylene glycol esters, luctylated esters, sorbttan and sorbitol esters, polysorbate.x, and sucrose esters. 

Figure D1.6.2 TLC-FID separation of lipids recovered from the gastric contents of a hooded seal pup. The mobile phase was 91 6 3 1 (v/v/v/v) hexane/ethyl acetate/diethyl ether/formic acid. Time refers to scanning time of the Chromarod. Abbreviations DG, 1,2-diglyceride FFA, free fatty acid MG, monoglyceride IS, internal standard TG, triglyceride. Reproduced from Ackman and Heras (1997) with permission from AOCS Press.

Partially scan the Chromarods (see Basic Protocol, step 9) from the top to a point just below the diglyceride peak to reveal neutral lipids. 

Chromarod FID peaks of sterols, diglycerides, monoglycerides, and polar lipids are narrower and sharper than peaks of triglycerides and free fatty acids when analyzed using either method described in this unit (see Basic Protocol and Alternate Protocol). Hydrogenation of total lipids (see Support Protocol) results in much sharper and narrower peaks, which in turn substantially improves the resolution between lipid classes. The accuracy and precision in quantitating lipid classes of vegetable oils and animal fats are expected to be better than those from marine lipids. 

The isolation of mutants in S. typhimurium by Rick and Osborn (11,12) and mutants in E. coli by Nishijima and Raetz (44) that accumulate the Lipid A precursor indicate that KDO synthesis and Lipid A synthesis are not coordinately controlled. The initial steps in the synthesis of the Lipid A precursor are totally unknown. The temperature sensitive mutants of E. coli isolated by Nishijima and Raetz (44) that are defective in phosphaditylglyc-erol phosphate synthesis at 42°C and accumulate the Lipid A precursors indicate that there is some relationship between the synthesis of phosphatidylglycerol and LPS. The reasons for the acu-cumulation of the Lipid A precursors in this E. coli mutant are not obvious. We have shown that CDP-diglyceride, one of the substrates for phosphatidylglycerol phosphate synthesis, is an inhibitor of D-arabinose-5-phosphate isomerase with an 1 value... 

J, 2, 4 ). The lipid component of lipoprotein was found to be made up of a diglyceride, bound by a thioether linkage to the mercapto... 

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. 

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