Phospholipids hydrogenation

Using diffuse reflectance Fourier transform infrared spectroscopy, Adhikari et al. studied the binding of oleic acid (88), triacylglycerol (89), and phosphatidylcholine (90) on silica gel at room temperature. Their interpretation was that oleic acid and triacylglycerols bind to silica surface hydroxyls via hydrogen bonding interactions between the carboxylate and ester carbonyls of these molecules, respectively. In contrast, phospholipids hydrogen bond to silica surface hydroxyls via the phosphate... 

U shape. This has profound significance on molecular packing in membranes and on the positions occupied by fatty acids in more complex molecules such as phospholipids. Trans double bonds alter these spatial relationships. Trans fatty acids are present in certain foods, arising as a by-product of the samration of fatty acids during hydrogenation, or hardening, of natural oils in the manufacture of margarine. An additional small... 

It has been proposed that the a-tocopheroxyl radical can be recycled back to tocopherol by ascorbate producing the ascorbyl radical (Packer etal., 1979 Scarpa et al., 1984). The location of a-tocopherol, with its phytyl tail in the membrane parallel to the fatty acyl chains of the phospholipids and its phenolic hydroxyl group at the memisrane-water interface near the polar headgroups of the phospholipid bilayer, enables ascorbate to donate hydrogen atoms to the tocopheroxyl radical. The suitability for ascorbate and tocopherol as chain-breaking antioxidants is exemplified (Buettner,... 

Hydrogen bonding and electrostatic interactions between the sample molecules and the phospholipid bilayer membranes are thought to play a key role in the transport of such solute molecules. When dilute 2% phospholipid in alkane is used in the artificial membrane [25,556], the effect of hydrogen bonding and electrostatic effects may be underestimated. We thus explored the effects of higher phospholipid content in alkane solutions. Egg and soy lecithins were selected for this purpose, since multicomponent mixtures such as model 11.0 are very costly, even at levels of 2% wt/vol in dodecane. The costs of components in 74% wt/vol (see below) levels would have been prohibitive. 

Most drug-like molecules dissolved in water form hydrogen bonds with the solvent. When such a molecule transfers from water into a phospholipid bilayer, the solute-water hydrogen bonds are broken (desolvation), as new solute-lipid H bonds form in the lipid phase. The free-energy difference between the two states of solvation has direct impact on the ability of the molecules to cross biological barriers. 

Figure 7.50 Hydrogen bonding/electrostatics scale based on phospholipid-alkane permeability differences A log Pe versus Pe (dodecane).

Biegel, C. M. Gould, J. M., Kinetics of hydrogen ion diffusion across phospholipid vesicle membranes, Biochemistry 20, 3474-3479 (1981). 

Haider SS, Hasan M, Islam F. 1980. Effect of air pollutant hydrogen sulfide on the levels of total lipids, phospholipids cholesterol in different regions of the guinea pig brain. Indian J Exp Biol 18 418-420. 

Hydrogen bonding and electrostatic interactions between the sample molecules and the phospholipid bilayer membranes are thought to play a key role in the transport of such molecules. When dilute 2% wt/vol phospholipid in alkane is used in the artificial membrane [15, 23], the effect of hydrogen bonding and electrostatic effects may be underestimated. 

Kimura M, Fukumoto K, Watanabe J et al (2004) Hydrogen-bonding-driven spontaneous gelation of water-soluble phospholipid polymers in aqueous medium. J Biomater Sci Polym Edn 15 631-644... 

In 1977, Kellogg and Fridovich [28] showed that superoxide produced by the XO-acetaldehyde system initiated the oxidation of liposomes and hemolysis of erythrocytes. Lipid peroxidation was inhibited by SOD and catalase but not the hydroxyl radical scavenger mannitol. Gutteridge et al. [29] showed that the superoxide-generating system (aldehyde-XO) oxidized lipid micelles and decomposed deoxyribose. Superoxide and iron ions are apparently involved in the NADPH-dependent lipid peroxidation in human placental mitochondria [30], Ohyashiki and Nunomura [31] have found that the ferric ion-dependent lipid peroxidation of phospholipid liposomes was enhanced under acidic conditions (from pH 7.4 to 5.5). This reaction was inhibited by SOD, catalase, and hydroxyl radical scavengers. Ohyashiki and Nunomura suggested that superoxide, hydrogen peroxide, and hydroxyl radicals participate in the initiation of liposome oxidation. It has also been shown [32] that SOD inhibited the chain oxidation of methyl linoleate (but not methyl oleate) in phosphate buffer. 

Hauser and Strauss [3.40] assumed the hydrogen bond between sucrose and phospholipid as the cause of the integrity of the unilamellar vesicles and showed, that enclosed ions cannot migrate to the surroundings. 

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