Fatty acid common structural feature

Hydrophobic and Hydrophilic Components of Membrane Lipids A common structural feature of membrane lipids is their amphipathic nature. For example, in phosphatidylcholine, the two fatty acid chains are hydrophobic and the phosphocholine head group is hydrophilic. For each of the following membrane lipids, name the components that serve as the hydrophobic and hydrophilic units (a) phos-phatidylethanolamine (b) sphingomyelin (c) galactosyl-cerebroside (d) ganglioside (e) cholesterol. 

Problem 19.4. What are the common structural features of the fatty acids used to synthesize saponifiable lipids in plants and animals (refer to Table 19-1) ... 

The connections between endoeannabinoids and eicosanoids occur in several areas. First, there is the obvious common structural feature based on arachidonic acid (eicosatetraeneoic acid) as well as other long-chain polyunsaturated aeids. In the case of the eicosanoids, all of the members are either cyclization or oxidation produets of arachidonic acid whereas in the endocannabinoids the fatty acid structure is preserved (Figure 8.1). 

Nitrosohydrazones from culture filtrates of Strepto-myces sp. SK 1894, e.g., T. B CnHijNjO, Mr 205.26, yellow powder, mp. 144-147 °C T. A C,H,9N)0, Mr 209.29, yellow powder, mp. 116-118°C. T. inhibit various acyl-CoA synthetases, e.g., arachidonoyl-CoA synthetase and the synthetases of longer-chain fatty acids the biosynthesis of acetyl-CoA remains unaffected. Common structural feature of the T. is the -N-hydroxy-l-triazene unit, bound to an unsaturated aliphatic chain. 

Mammalian proteins are the targets of a wide range of covalent modification processes. Modifications such as glycosylation, hydroxylation, and fatty acid acylation introduce new structural features into newly synthesized proteins that tend to persist for the lifetime of the protein. Among the covalent modifications that regulate protein function (eg, methylation, adenylylation), the most common by far is phosphorylation-dephos-phorylation. Protein kinases phosphorylate proteins by... 

The close packing of the acyl groups associated with the inclination of the lipid A backbone with respect to the fatty acid orientation seems to constitute a common and characteristic feature of the lipid A conformation. This specific (endotoxic) conformation is very likely to influence greatly the tendency of the amphiphilic lipid A to adopt peculiar supramolecular structures. 

Polyketide synthases, fatty acid synthases, and non-ribosomal peptide synthetases are a structurally and mechanistically related class of enzymes that catalyze the synthesis of biopolymers in the absence of a nucleic acid or other template. These enzymes utilize the common mechanistic feature of activating monomers for condensation via covalently-bound thioesters of phosphopantetheine prosthetic groups. The information for the sequence and length of the resulting polymer appears to be encoded entirely within the responsible proteins. 

Then, with the help of a colleague, Asher Mandelbaum, at the Technion in Haifa, we got a high-resolution mass spectrum, which indicated that the molecule contains a nitrogen, certainly not a common feature in fatty acids. However, the structure was now close at hand. Some more mass spectra and a better nuclear magnetic resonance (NMR) led to a final formulation of the ligand as arachidonoyl ethanol amide (Devane, Hanus, et al., 1992). 

The structure in the micellar region of the phase diagrams of potassium soaps has been analysed by Reiss-Husson and Luzzati (1969) using X-ray methods. A common feature in soaps of saturated fatty acids is that spherical micelles exist at low concentrations, and at increased concentrations a transition into rod micelles occurs. Sodium oleate, however, was found to give rod-shaped micelles at all concentrations. The micellar association and phase behaviour have been reviewed by Wenner-strom and Lindman (1979) and Lindman and Wennerstrom (1980). 

The common structure of vegetable oils discussed here is that of aliphatic triglycerides (Scheme 1.1), in which the fatty acid chains Ri, Ri and R3 are most often identical, but can also vary, within a given molecule. The length of the fatty-acid chain is 14-22 carbon atoms, but most members bear 16 or 18 units. The other important feature of these linear aliphatic motifs is the possible presence of C=C unsaturations, which range from 0 to 3. More than 1,000 fatty acids have been identified, but only 20 are present in appreciable quantities in vegetable oils [2, 3]. 

There are a number of polymers, notably hydrogenated castor oil and its derivatives, polyamides (Chapter 15) and polyamide-oil or polyamide-alkyd reaction products (Chapter 12), which can be used to impart non-Newtonian viscosity to paints based on non-polar (mainly aliphatic hydrocarbon) solvents. The thickening mechanisms of polymeric additives are not fully established, but the resins have in common the following features borderline solubility in the paints in which they are used and chemical structures involving lengthy soluble non-polar chains (e.g. fatty portions of fatty acids) and polar groups, e.g. -OH, -CONH- and -COOH. 

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