Palmitate structure

Write the chemical equation for preparing sodium soap from glyceryl oleate and glyceryl palmitate. Structural formulae of these compounds are given below. 

Spermaceti is a wax obtained from the sperm whale It contains among other materials an ester known as cetyl palmitate which is used as an emollient in a number of soaps and cosmetics The systematic name for cetyl palmi tate IS hexadecyl hexadecanoate Write a structural formula for this substance... 

Draw the structures of (a) all the possible triacylglycerols that can be formed from glycerol with stearic and arachidonic acid, and (b) all the phosphatidylserine isomers that can be formed from palmitic and linolenic acids. 

Spermaceti, a fragrant substance from sperm whales, was much used in cosmetics until it was banned in 1976 to protect the whales from extinction. Chemically, spermaceti is cetyl palmitate, the ester of cetyl alcohol (u-ClrtH33OH) with palmitic acid. Draw its structure. 

Palmitic acid, structure of, 1062 Palmitoleic acid, structure of, 1062 PAM resin, solid-phase peptide synthesis and, 1037 Para (m), 519 Paraffin, 91 Parallel synthesis, 586 Parent peak (mass spectrum), 410 Partial charge, 36 Pasteur, Louis, 297, 307... 

In the x-ray structure of rhodopsin, an amphipathic helix runs parallel to the membrane from the intracellular end of TM-VII beneath the seven-helical bundle to the other side of TM-I and TM-II. At this point, one or more Cys residues are often found and are known to be subject to a dynamic posttranslational modification with palmitic acid residues. Like the phosphorylation event, the palmitoylation process appears to be dynamically regulated by receptor occupancy and is also involved in the desensitization phenomenon. The two posttranslational modifications can influence each other. For example, the conformational constraint induced by palmitoylation may alter the accessibility of certain phosphorylation sites. Like the phosphorylation process, the functional consequences of palmitoylation also appear to vary from receptor to receptor. 

Soaps are composed of sodium salts of various fatty acids. These acids include those with the general structure CH3-(CH2) -COOH where n = 6 (caprylic acid), 8 (capric acid), 10 (lauric acid), 12 (myristic acid), 14 (palmitic acid), and 16 (stearic acid). Oleic acid (CH3-(CH2)7-CH=CH-(CH2)7-COOH) and linoleic acid (CH3-(CH2)4-CH=CH- H2-CH=CH-(CH2)7-COOH) are also common soap ingredients. These sodium salts readily dissolve in water, but other metal ions such as Ca2+ and Mg2+ form precipitates with the fatty acid anions. For example, the dissolution of the sodium salt of lauric acid and the subsequent formation of a precipitate of the lauric acid anion with calcium ion is given by... 

Figure 13.16.4 The molecular structure of the mixed fatty acid palmitodiolein, which is triglyercide of two esters of oleic acid and one of palmitic acid.

Lerche, M.H. and Poulsen, F.M. (1998) Solution structure of barley lipid transfer protein complexed with palmitate. Two different binding modes of palmitate in the homologous maize and barley nonspecific lipid transfer proteins. Protein Science 7, 2490-2498. 

Figure 11.1 Structures of commonly occurring saturated fatty acids (i) myristic acid, Ci4 o (ii) palmitic acid, C s-.o (iii) stearic acid, Ci8 0.

Figure 12.2 Structure of waxes. The general structure of a wax is shown in which n and m are usually between 8 and 18. The structure of hexadecyl hexadecanoate (cetyl palmitate), a wax found in sperm whale oil, is shown. This is an ester of hexadecanoic (palmitic) acid and hexadecanol (cetyl alcohol).

Lipid transfer peptides and proteins occur in eukaryotic and prokaryotic cells. In vitro they possess the ability to transfer phospholipids between lipid membranes. Plant lipid transfer peptides are unspecific in their substrate selectivity. They bind phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and glycolipids. Some of these peptides have shown antifungal activity in vitro The sequences of lipid transfer proteins and peptides contain 91-95 amino acids, are basic, and have eight cysteine residues forming four disulfide bonds. They do not contain tryptophan residues. About 40% of the sequence adopts a helical structure with helices linked via disulfide bonds. The tertiary structure comprises four a-helices. The three-dimensional structure of a lipid transfer peptide from H. vulgare in complex with palmitate has been solved by NMR. In this structure the fatty acid is caged in a hydrophobic cavity formed by the helices. 

The common fatty acids have a linear chain containing an even number of carbon atoms, which reflects that the fatty acid chain is built up two carbon atoms at a time during biosynthesis. The structures and common names for several common fatty acids are provided in table 18.1. Fatty acids such as palmitic and stearic acids contain only carbon-carbon single bonds and are termed saturated. Other fatty acids such as oleic acid contain a single carbon-carbon double bond and are termed monounsaturated. Note that the geometry around this bond is cis, not trans. Oleic acid is found in high concentration in olive oil, which is low in saturated fatty acids. In fact, about 83% of all fatty acids in olive oil is oleic acid. Another 7% is linoleic acid. The remainder, only 10%, is saturated fatty acids. Butter, in contrast, contains about 25% oleic acid and more than 35% saturated fatty acids. 

This structure shows a triglyceride with three identical saturated fatty acids. Tripalmitin, in which all fatty acids are palmitic acid (n = 14), provides one example of a fat. Triolein is an oil containing only oleic acid moieties esterified to glycerol. In contrast to these two examples, it is by no means necessary that the three fatty acid groups be derived from only one fatty acid. For example, we might have a triglyceride that contains one saturated fatty acid, say palmitic acid, one monounsaturated fatty acid, say oleic acid, and one polyunsaturated fatty acid, perhaps arachidonic acid. 

Figure 5.1 The structure of a glycerophospholipid. A simple diagram showing the charges on the head group. In this struction, palmitic and oleic acids, provide the hydrophobic component of the phospholipids and choline (and four bases) and the phosphate group provide the hydrophilic head. The unsaturated fatty acid, oleic acid, provides a kink in the structure and therefore some flexibility in the membrane structure which allows for fluidity. The more unsaturated the fatty acid, the larger is the kink and hence more fluidity in the membrane. Cholesterol molecules can fill the gaps left by the kink and hence reduce flexibility. Hydroxyl groups on the bases marked are those that form phosphoester links. Choline and inositol may sometimes be deficient in the diet so that they are, possibly, essential micronutrients (Chapter 15).

The provision of fat-soluble vitamins and lipids is difficult, if not impossible, in various diseases. This is especially true for diseases that are accompanied by a lot of oxidative stress, for example, mucoviscidosis. The requirements of fat-soluble antioxidative substances are certainly high in these cases and can barely be covered by intramuscular injections because fat-soluble vitamins can hardly, if at all, be absorbed from oily preparations. Alternatively, the vitamins can administered via the buccal mucosa the fat-soluble substances have to be packaged in such a way that they can be transported in a watery compartment and are thus able to largely dissolve in the saliva. When they have an adequate size, they can then penetrate the buccal mucosa. One approach is the development of the so-called nanocolloids, that is, particles with a polar nucleus, in which the fat-soluble vitamin is dissolved, and an apolar wrapping (monolayer). This structure makes an oral application of fat-soluble substances possible. First tests demonstrated that vitamin A palmitate, a-tocopherol, as well as coenzyme Qio are thus able to enter the systemic circulation via the buccal mucosa. 

D. Additions to and modifications of palmitate allow synthesis of many structurally distinct fatty acids. 

Interest has been shown in using derivatives of ascorbic acid as antioxidants. One such compound is ascorbyl palmitate. In the structure of ascorbyl palmitate, the 2- and 3-positions are occupied by hydroxyl groups the 6-position contains the substituted fatty acid. Other derivatives, synthesized by Seib and associates were ascorbate-2 phosphate and ascorbate 2-triphosphate (27). Both of these compounds were reported to inhibit lipid oxidation in ground meat as measured by chemical means (2). Ascorbate-2-phosphate was also found to inhibit MFD in beef as measured by sensory means (2). The ascorbate-2-triphosphate was not tested as an inhibitor of MFD in this study, but... 

It is pertinent to note here the observed increase in the value of the structure-sensitive parameter p from 1 to 2. This implies that the architecture of the sodium caseinate aggregates, as modified by interaction with the surfactant, becomes generally more open, despite the inferred collapse of their constituent protein nanoparticles. In contrast, a shell-like aggregation structure can be inferred for the self-assembly of sodium caseinate as a result of its interaction with the non-ionic surfactant PGE (this surfactant is based on a mixture of the esters of stearic and palmitic acids in chemical combination with polyglycerol (Krog, 1997)). 

Figure 2.24 Structure of lactitol and its conversion to lactyl palmitate.

The biosynthesis of fatty acids such as palmitate thus requires acetyl-CoA and the input of chemical energy7 in two forms the group transfer potential of ATP and the reducing power of NADPH. The ATP is required to attach C02 to acetyl-CoA to make malonyl-CoA the NADPH is required to reduce the double bonds. We return to the sources of acetyl-CoA and NADPH soon, but first let s consider the structure of the remarkable enzyme complex that catalyzes the synthesis of fatty acids. 

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