Fatty acids ester-bound

In addition to these numerous results, two other points are discussed by the authors fatty acid speciation and oil identification. These two aspects are developed in another publication written by the same authors [Keune et al. 2005]. The fatty acid speciation is based on the positive ion ToF-SIMS analysis and aims to prove if the fatty acids detected exist as free fatty acids, ester bound fatty acids or metal soaps. On account of the study of different standards, it is shown that when free fatty acids are present, the protonated molecular ion and its acylium ([M-OH]+) ion are detected. In cases of ester-bound fatty acid only the... 

Chem. Descrip. High m.w. aliphatic fatty acid esters bound to chemically inert filers... 

A variety of cellular and viral proteins contain fatty acids covalently bound via ester linkages to the side chains of cysteine and sometimes to serine or threonine residues within a polypeptide chain (Figure 9.18). This type of fatty acyl chain linkage has a broader fatty acid specificity than A myristoylation. Myristate, palmitate, stearate, and oleate can all be esterified in this way, with the Cjg and Cjg chain lengths being most commonly found. Proteins anchored to membranes via fatty acyl thioesters include G-protein-coupled receptors, the surface glycoproteins of several viruses, and the transferrin receptor protein. 

Breithaupt, D.E. and Schwack, W., Determination of free and bound carotenoids in paprika (Capsicum annuum L.) by LC/MS, Fur. Food Res. Technol., 211, 52, 2000. Philip, T. and Berry, J.W., A process for the purification of lutein-fatty acid esters from marigold petals, J. Food ScL, 41, 163, 1976. 

Hydroxylaminolysis, treatment with stronger alkali (0.5 m NaOH, 2 h, 100°C) and alkaline methanolysis (0.25 m NaOMe, 1 h, 50°C) lead to complete O-deacylation of LPS and lipid A (176). Particularly in the case of alkaline methanolysis, ester-linked 3-acyloxyacyl residues undergo, in addition to transmethylation, a -elimination reaction, whereby the (R)-3-hy-droxy fatty acid ester is first transformed into the a,/ -unsaturated and then into the (S.-R -methoxy fatty acid methyl ester. The acyl substituent, on the other hand, is eliminated in the form of the free fatty acid (176). In fact, the presence of a 3-methoxyacyl derivative in the fatty acid spectrum of a given LPS is a strong indication for the presence of an ester-bound 3-acyloxyacyl... 

Because the polar hydroxyls of glycerol and the polar carboxylates of the fatty acids are bound in ester linkages, triacylglycerols are nonpolar, hydrophobic molecules, essentially insoluble in water. Lipids have lower specific gravities than water, which explains why mixtures of oil and water (oil-and-vinegar salad dressing, for example) have two phases oil, with the lower specific gravity, floats on the aqueous phase. 

We should note, however, that incorporation of a substrate into a micelle will accelerate its reaction with a micelle counterion only if the substrate is bound at the micellar surface, since ionic reagents cannot, apparently, penetrate into the micellar core. Thus, the hydroxyl ion-catalyzed hydrolysis of long-chain fatty acid esters of 3-nitro-4-hydroxybenzenesulfonic acid was inhibited by incorporation into micelles no matter whether these were uncharged, anionic, or cationic (68). 

The mechanism by which xenobiotic alcohols or esters are converted to fatty acid esters has not been studied. They could be formed by the action of lyase enzymes in the presence of fatty acid glyceryl esters, as in the conversion of farnesol to farnesol fatty acid esters (150). Some lipolytic acyl hydrolase enzymes from plants readily catalyze the transfer of lipid-bound fatty acids to low MW alcohol acceptors (150.151) and enzymes of this class could be responsible for the occasional formation of fatty acid conjugates of xenobiotic alcohols. Mechanisms involving fatty acid acyl CoA, phospholipids, or direct esterification with fatty acids might also be involved (1 ). 

The n-3 PUFAs are important components of cell membranes throughout the body, as they are incorporated into the phospholipids that form cell membranes. Each phospholipid molecule is comprised of a headgroup to which fatty acid esters are bound. There are two binding positions, termed 5 -l and sn-l. The acyl chains that bind to these headgroups interact with other chains in neighboring phospholipid molecules within the bilayer, and the level of chain interaction determines the biophysical properties of the membrane. The sn-l position is usually occupied by a saturated fatty acid the sn-2 position is usually occupied by a relatively unsaturated fatty acid chain. 

Cao L, Eischer A, Bornscheuer UT et al. (1997) Lipase-catalysed solid phase synthesis of sugar fatty acid esters. Biocatal Biotransfor 14 269-283 Cao L, van Langen L, Sheldon, R (2(X)3) Immobilised enzymes carrier-bound or carrier-free Curr Opin Biotechnol 14 1-8... 

Alcohols are usually esterified with fatty acids of similar structure. The characteristic structure is expressed by formula 3-42. The compound name is formed by the radical names of the alcohol and the bound acid. For example, ceryl cerotate is the ester of cerotic acid with ceryl alcohol. The main wax ester on the surface of sunflower seeds is ceryl cerotate. The main surface wax esters of apples and cabbage leaves are ceryl palmitate and ceryl stearate. The constituents of the epicuticular wax of apple fruits are also Cig-C26 fatty acid esters of (E)- and (Z)-p-coumaryl alcohol. The fatty acid esterification occurs at the y-hydroxyl group rather than at the 4-hydroxyl on the phenyl ring. 

Diterpenic alcohols Diterpenic alcohols are present in nature as free compounds or bound in fatty acid esters and glycosides. They have no significance as flavourings, but may be precursors of flavour-active products. A number of diterpenoids are biologically active substances. Diterpenic alcohols known as gibberellins are found universally in plant tissues, and act as plant hormones. 

According to the invention, it has been found that mixtures of the above mentioned glycerol fatty acid esters, in particular of glycerol bisstearate, with polybutylene terephthalate are significantly less volatile than the volatility of the separate compounds would suggest. Without being bound by any particular the-... 

When most lipids circulate in the body, they do so in the form of lipoprotein complexes. Simple, unesterified fatty acids are merely bound to serum albumin and other proteins in blood plasma, but phospholipids, triacylglycerols, cholesterol, and cholesterol esters are all transported in the form of lipoproteins. At various sites in the body, lipoproteins interact with specific receptors and enzymes that transfer or modify their lipid cargoes. It is now customary to classify lipoproteins according to their densities (Table 25.1). The densities are... 

Fujiwara et al. used the CMC values of sodium and calcium salts to calculate the energetic parameters of the micellization [61]. The cohesive energy change in micelle formation of the a-sulfonated fatty acid methyl esters, calculated from the dependency of the CMC on the numbers of C atoms, is equivalent to that of typical ionic surfactants (Na ester sulfonates, 1.1 kT Ca ester sulfonates, 0.93 kT Na dodecyl sulfate, 1.1 kT). The degree of dissociation for the counterions bound to the micelle can be calculated from the dependency of the CMC on the concentration of the counterions. The values of the ester sulfonates are also in the same range as for other typical ionic surfactants (Na ester sulfonates, 0.61 Ca ester sulfonates, 0.70 Na dodecyl sulfate, 0.66). 

FIGURE 9.1 GC/MS of total methyl esters of fatty acids standards and single fractions after PLC. Abbreviations first number (18 or 20) = number of carbon atoms in the chain second number (0 to 5) = number of double bounds n = normal chain i =isoacid ai = anteisoacid m-br =multi-branched acid. (From Rezanka, T., J. Chromatogr. A, 727, 147-152, 1996. With permission.)... 

Furthermore, enzymes that quantitatively liberate ester-bound fatty acids of lipid A are known. Such esterases are present in the amoebae Dictyoste-liurn discoideum (177-179) and Acanthamoeba castellanii (178). Selective... 

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