Unsaturated C-18 fatty acids

Six-carbon compounds such as hexanal, 3Z-, and 2E-hexenal at high concentrations were detected in ruptured tissue of apples, grapes, and tomatoes (Schreier and Lorenz, 1981). These compounds, when they occur, are only in trace amounts in intact plant cells. Aliphatic C-6 components, which contribute to the green note of fruits, are formed from unsaturated C-18 fatty acids by enzymatic activity after cellular disruption. LOX is involved in the reaction (Galliard and Matthew, 1977). 

Fatty polyamide (Versamid , oldest of many trade names). A polymer formed by the condensation of a dibasic acid having a bulky side group and from 13- to 21-carbon chains, or the dimmer acids, C-36, with di- or polyamines. The commercially important dimmer acids are addition products of unsaturated C-18 fatty acids and can take several forms, giving different structures to the polyamides. They are used in hot-melt adhesives, inks, as epoxy flexibilizers and, in amine form, as curing agents for epoxies. Skeist I (ed) (1990, 1977, 1962) Handbook of adhesives. Van Nostrand Reinhold, New York. 

From substrate specificity studies (23,24), it seems that DS5 hydratase hydrates a specific carbon position of the unsaturated fatty acid substrates. To clarify this point and the effect of substrate carbon chain length on the strain DS5 hydratase activity, we studied the hydration of mono-, di-, and triunsaturated C-18 fatty acids as well as other carbon chain length monounsaturated fatty acids. 

Kato, T, Y. Yamaguchi, N. Abe, T. Uyehara, T. Namai, M. Kodama, and Y. Shiohara, Structure and Synthesis of Unsaturated Trihydroxy C-18 Fatty Acids in Rice Plant Suffering from Rice Blast Disease, Tetrahedron Lett. 26 2357-2360 (1985). 

Contains 1% unidentified unsaturated C o fatty acids and 3.6% unidentified fatty m id whose retention time on GLC comes between those of 18 1(9) and 18 2(9,12). Grown on synthetic medium containing cr-methyl-n-butyrate, which promotes formation of branched-chain fatty acids. Presence of triparanol in medium has a more marked effect on fatty acid composition. 

Reviews of fungal fatty acid composition (, 7, ) reveal that their primary constituents are 12- to 20-carbon chain length unbranched compounds, with even-numbered chains predominant. Both saturated and unsaturated compounds occur, with palmltolelc (C-16 l), oleic (C-18 l), llnolelc (C-18 2) and llnolenlc (C-18 3) acids the most common unsaturated moieties ( ). As with most naturally occurring fatty acids (9), monounsaturated compounds usually contain a els oleflnlc bond and polyunsaturated acids have methylene-interrupted els double bonds. Although rare In occurrence and subjected to limited study, branched chains, hydroxy, oxo and epoxy acids are also synthesized ( 5). Lists of the structures of unusual fatty acids which can be employed In structure activity studies are presented In detail elsewhere (9-14). 

Tables and figures present means and their standard deviations (M + m). In Figures 2 and, correlations between unsaturation coefficients of C 18 and C 20 fatty acids and the rates of NAD-dependent substrate oxidation are presented they were calculated using Statistica v. 6 software for Windows.

More recently, McLean et al. [20] determined the pKa of individual fatty and resin acids by titration using a similar titration method to that of Kanicky and Shah [19]. The values, which they termed colloidal p/fa-values , were slightly lower than those obtained by Kanicky and Shah, especially for the unsaturated C-18 acids. The differences were, however, not discussed. Resin acids gave pKa-values of 6.2-13, values that are in the range of earlier reported values [21-23]. 

The dimer acids [61788-89-4] 9- and 10-carboxystearic acids, and C-21 dicarboxylic acids are products resulting from three different reactions of C-18 unsaturated fatty acids. These reactions are, respectively, self-condensation, reaction with carbon monoxide followed by oxidation of the resulting 9- or 10-formylstearic acid (or, alternatively, by hydrocarboxylation of the unsaturated fatty acid), and Diels-Alder reaction with acryUc acid. The starting materials for these reactions have been almost exclusively tall oil fatty acids or, to a lesser degree, oleic acid, although other unsaturated fatty acid feedstocks can be used (see Carboxylic acids. Fatty acids from tall oil Tall oil). 

The melting points of even-numbered-carbon fatty acids increase with chain length and decrease according to unsaturation. A triacylglycerol containing three sam-rated fatty acids of 12 carbons or more is solid at body temperature, whereas if the fatty acid residues are 18 2, it is liquid to below 0 °C. In practice, natural acylglyc-erols contain a mixture of fatty acids tailored to suit their functional roles. The membrane lipids, which must be fluid at all environmental temperatures, are... 

Unsaturated fatty acids usually contain a cis double bond at position 9 or 12—e.g., linoleic acid (18 2 9,12). As with saturated fatty acids, degradation in this case occurs via p-oxida-tion until the C-9-ds double bond is reached. Since enoyl-CoA hydratase only accepts substrates with trans double bonds, the corresponding enoyl-CoA is converted by an iso-merase from the ds-A, cis- A isomer into the trans-A, cis-A isomer [1]. Degradation by p-oxidation can now continue until a shortened trans-A, ds-A derivative occurs in the next cycle. This cannot be isomerized in the same way as before, and instead is reduced in an NADPH-dependent way to the trans-A compound [2]. After rearrangement by enoyl-CoA isomerase [1 ], degradation can finally be completed via normal p-oxidation. 

A very polar phase such as carbowax is generally only used for samples requiring a high degree of polar discrimination for adequate separation or retention. An example of this is in the analysis of fatty acids with differing degrees of unsaturation. On a non-polar column such as BPX-5, a series of C-18 acids such as stearic, oleic, linoleic and linolenic acids, which contain respectively 0, 1,2 and 3 double bonds, overlaps extensively. However, on polar columns such as carbowax they are separated. 

Figure 4.2 GC/MS analysis of methyl esters prepared from a whole cell lipid extract of the YEpOLEX-HzPGDsI-transformed ole1 strain of S. cerevisiae total ion spectrum of fatty acid methyl esters resolved by capillary GLC. The culture was grown in liquid complete medium (YPD) at 30°C to a density of 2 x 107 cells/ml prior to extraction and methylation. The external mass standard nonadecanoic acid methyl ester (19 Me) was added to the cell pellet prior to extraction. Peaks corresponding to Z9-16 Me and Z9-18 Me reflect trace amounts of unsaturated fatty acids in the growth medium. (Reproduced with permission from Rosenfield et at, 2001. 2001 by Insect Biochemistry and Molecular Biology.)...

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