Saturated lecithins

The inclusion of/3-carotene into lipid membranes formed with saturated lecithin (DPPC) increases motional freedom of lipid molecules in the ordered state of the membrane (Jezowska et al., 1994). 

The polymer is expected to be at least occasionally cross-linked Since the polymer chains are very flexible, the amphiphilic polybutadienes represent a better approach to biological membranes than the corresponding polydiacetylenes In particular of interest are partially polymerized membranes, which consist of polymerizable butadiene lecithines and saturated lecithines (e.g. dimyristoyl-lecithin, DMPC). While vesicles of DMPC exhibit a typical ripple structure, the surface of the polymerized vesicles appears homogeneous. Electron micrographs of mixed vesicles show a phase separation, indicated by the simultaneous presence of regions with a smooth surface due to the polymer, and rippled regions due to DMPC Instead of... 

Saturated lecithins can be separated from the mercuric acetate adducts of unsaturated lecithins, on silica gel G, using chloroform-methanol-water (70 +30 + 4) [14]. 

Thin-layer chromatographic separation of saturated lecithins from the adducts of the corresponding unsaturated compounds has facilitated enzymatic structure analysis of egg-, soya- and milk lecithins and also the gas chromatographic determination of their fatty acid composition [14]. 

Saturated lecithins and the three types of aldehydic cores obtained by reductive ozonolysis of unsaturated lecithins can be separated through reversed phase partition chromatography [168]. Fig. 147 shows photo-densitometric curves from thin-layer chromatograms of fission products derived from the lecithins of egg, bovine spinal cord, soya bean and wheat germ. 

Many of these peptidolipids have amphiphilic properties. This is illustrated by the protoplast-bursting activity of surfactin (93) or by the strong lysing activity of iturin A (but not iturin C) and bacillomycin L on erythrocytes (166), or the disruption of the outer membrane of Escherichia coli by EM 49 (152). Likewise antibiotics of the iturin group increased the size of small unilamellar vesicles of saturated lecithins (167). Differences in the balance between the hydrophobicity of the hydrocarbon chain and the polarity of the peptide moiety might explain the differences of action of iturin A, mycosubtilin and bacillomycin on Micrococcus luteus cells and protoplasts (168). 

Hydrogena.tlon. Lecithin can be hydrogenated. The resulting lecithins have only saturated fatty acid residues (palmitic or stearic acid) and are more or less colorless and crystalline. 

The yolk is separated from the white by the vitelline membrane, and is made up of layers that can be seen upon careful examination. Egg yolk is a complex mixture of water, Hpids, and proteias. Lipid components iaclude glycerides, 66.2% phosphoUpids, 29.6% and cholesterol [57-88-5] 4.2%. The phosphohpids consist of 73% lecithin [8002 3-5] 15% cephahn [3681-36-7], and 12% other phosphohpids. Of the fatty acids, 33% are saturated and 67% unsaturated, including 42% oleic acid [112-80-1] and 7% linoleic acid [60-33-3]. Fatty acids can be changed by modifying fatty acids ia the laying feed (see... 

In this connection it is interesting to recall Kremer s experiments. By means of a spectroscopic method, Kremer demonstrated that when air saturated with an odoriferous substance such as pyridine or camphor is bubbled through a liquid containing a lipoid—such as a suspension of lecithin of a fatty animal tissue in Ringer s solution—more of the odoriferous substance is adsorbed than when the saturated air passes through water only. 

Fig. 21.14. In vitro dissolution rate versus saturation solubility for candersartan cilexitil in different concentrations of sodium taurocholate lecithin ratio 2.5 1.

LEH is primarily composed of a combination of saturated high-carbon phospholipids and cholesterol. Synthetic phospholipids replaced hydrogenated soy lecithin when the latter was found to induce several untoward biological responses (40). Current choice of a saturated high-carbon phospholipid is mostly between distearoyl phosphatidylcholine (DSPC, 55°C) and... 

Fig. 10. A plot of the maximal relative activity (uRmax) of /3 hydroxybutyrate dehydrogenase-lecithin mixtures versus the number of carbon atoms in the saturated fatty acid side chains of the lecithins.

Phospholipid vesicles (and bilayers) composed of phospholipids with well-defined fatty acid side chains undergo a sharp transition from a crystallinelike state to an amorphous state as the temperature is raised.107 The transition temperature depends on the nature of the fatty acid side chains. For example, for C12 saturated fatty acid chains on lecithin the transition temperature is 0° and for C18 saturated fatty acid chains it is 58°C for unsaturated lecithins the transition temperature is below zero.107 For real membranes sharp phase transitions are not observed, because of the heterogeneous composition of the membrane. In the case of /3 hydroxybutyrate dehydrogenase, the enzymic activity apparently is not influenced by this phase transition as judged by the temperature dependence of the reaction rate. However, for some membrane-bound proteins, a plot of the reaction rate versus the reciprocal temperature... 

Lecithins and related phospholipids usually contain a saturated fatty acid in the C-l position but an unsaturated acid, which may contain from one to four double bonds, at C-2. Arachidonic acid is often present here. Hydrolysis of the ester linkage at C-2 yields a l-acyl-3-phosphoglycerol, better known as a Iysophosphatidylcholine. The name comes from the powerful detergent action of these substances which leads to lysis of cells. Some snake venoms contain phospholipases that form Iysophosphatidylcholine. Lysophosphatidic acid (l-acyl-glycerol-3-phosphate) is both an intermediate in phospholipid biosynthesis (Chapter 21) and also a signaling molecule released into the bloodstream by activated platelets.15... 

Glycerophospholipids contain a glycerol skeleton to which two fatty acids are esterified saturated fatty acids occupy mostly sn-position 1, whereas unsaturated fatty acids are mainly present on sn-position 2. The third hydroxyl is linked to a phosphate group to which an organic base is mostly esterified (Fig. 1). The most important components of soybean lecithin are phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). Phosphatidic acid (PA) may become important due to the presence of phospholipase D this enzyme slowly converts PC into PA in vegetable lecithins. Phosphatidylserine (PS), phosphatidylglycerol (PG), and lyso-phosphatidylcholine (LPC) are known as minor components lysophospholipids contain only one acyl group per molecule. Besides, ether phospholipids occur in which one or both fatty acyl... 

Lau et al. (2) have used electrophoresis and 31P NMR to estimate divalent cation adsorption potentials and the fraction of phosphorous nuclei whose magnetic resonance is affected by the presence of divalent cobalt. Although they see the same preference for solid vs. melted chains and the preference of (saturated chain) DPPC and DMPC for Ca2+ over Mg2, they note no similar ion preference by egg lecithin. They used... 

Naylor et al. (1993) studied the ability of lecithin to modify the rate and mechanism of dissolution of hydrocortisone in the presence of sodium taurocholate (NaTC) solutions. They found that in the presence of lecithin, the CMC of NaTC dropped owing to the more effective solubilization capacity of the mixed micelle. Furthermore, the CMC value dropped more on saturation with hydrocortisone, implying some interaction between hydrocortisone and the NaTC/lecithin micelles. These results indicated that in the NaTC-only system, wetting effects predominated dissolution, whereas in the NaTC/lecithin system, the dissolution rate of hydrocortisone was enhanced mainly through solubilization. 

Avocado produces a rather viscous oil that penetrates the upper skin layers well and is beneficial for dry skin and is often found in sun preparations. It is versatile, with applications ranging from soothing nappy rash to an ideal choice for damaged, dry and mature skin. It is a mixture of monounsaturated and saturated fatty acids, with oleic (60-70%), linoleic (8-15%), palmitoleic (4-7%), linolenic (2%), palmitic (12-16%) and stearic (2%). Vitamins A, B and D are found along with lecithin. Lecithin is one of the major phospholipids (a lipid combined with a phosphate group) of the body. Phospholipids are vital chemicals needed in the body for structural and metabolic functions. 

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