Fatty acid mimics

In the first of these sections, we will discuss a broad selection of examples related to organic reaction control, catalyst design, fatty acid mimics, conformations of biopolymers, structure of oligosaccharides that constitute part of the bacteria cell walls, and initiation of enzymaticprocesses associated with sensing hypoxia. Remarkably, each example from this diverse array originates from a common stereoelectronic source, the gauche effect... 

The few examples of deliberate investigation of dynamic processes as reflected by compression/expansion hysteresis have involved monolayers of fatty acids (Munden and Swarbrick, 1973 Munden et al., 1969), lecithins (Bienkowski and Skolnick, 1974 Cook and Webb, 1966), polymer films (Townsend and Buck, 1988) and monolayers of fatty acids and their sodium sulfate salts on aqueous subphases of alkanolamines (Rosano et al., 1971). A few of these studies determined the amount of hysteresis as a function of the rate of compression and expansion. However, no quantitative analysis of the results was attempted. Historically, dynamic surface tension has been used to study the dynamic response of lung phosphatidylcholine surfactant monolayers to a sinusoidal compression/expansion rate in order to mimic the mechanical contraction and expansion of the lungs. 

Fatty acid oxidation defects often produce recurrent disturbances of brain function [4, 8]. Drowsiness, stupor and coma occur during acute metabolic crises and mimic the Reye s syndrome phenotype. The neurological symptoms have been attributed to hypoglycemia, hypoke-tonemia and the deleterious effects of potentially toxic... 

It has been found that the catalytic activity of PKC is enhanced by a lipid component of the cell membrane, namely phosphatidylserine. This activity is further stimulated by sn-1,2-diacylglycerol. Oleic acid also activates the enzyme in the presence of 1,2-diacylglycerol, and thus it is presumed to mimic phosphatidylserine. In order to identify that modulating binding site for oleic acid on PKC, a photoaffinity analogue was devised. A carbene generating photophore, diazirine was placed in the apolar terminus of the unsaturated fatty acid ligand (30, Fig. 12). The synthesis and the photochemical activation properties were reported by Ruhmann and Wentrup [113]. 

To mimic nature in its irreversible monolipidation of proteins by N-myristoylation and S-prenylation, peptides are N-acylated with fatty acids or N-alkylated with linear or branched, saturated or unsaturated aliphatic chains as well as by incorporation of newly synthesized lipo-amino acids. 

The fatty acid-like leukotrienes derived from the addition of glutathione to products of the lipoxygenase branch of the arachidonic cascade are closely associated with manifestations of asthma. Many compounds designed to antagonize leukotrienes at the receptor level incorporate long alkyl chains to mimic the leukotrienes backbone in addition to the sulfur-containing moieties that stand in for glutathione. The reaction... 

Norephedrine and ephedrine mimic and stimulate the release of the adrenal hormones norepinephrine and epinephrine. Norephinephrine raises heart rate and epinephrine stimulates carbohydrate metabolism resulting in an increased metabolic rate, fatty acids release from lipocytes (fat cells), and a protein sparing effect. Caffeine simply prolongs the effect. 

Bioethanol is suitable for internal combustion engines that run on gasoline. Similarly, biodiesel is designed for diesel engines. Biodiesel is a fuel manufactured from various oils and fats. These acids are chemically transformed to fatty acid methyl esters. By blending the fatty acid methyl or ethyl esters in the right proportions, the properties of the fuel can be influenced [59] and potentially mimic the properties of petrochemically derived diesel. Biofuel efficiency generally is the same as for fossil-derived diesel fuel [59]. 

A role for cyclic AMP as a mediator for the actions of prolactin has been proposed, but the bulk of the evidence available suggests that it is not directly involved. It is possible that levels of cyclic AMP-dependent protein kinase are limiting, rather than cyclic AMP itself, and that these can be increased by prolactin, presumably by induction of the appropriate genes [67]. Cyclic AMP derivatives do not mimic the actions of prolactin in in vitro systems. Indeed, they may inhibit some actions of the hormone, including stimulation of synthesis of milk proteins, fatty acids, DNA and RNA in mammary gland explants [79-81]. 

Betapol , a human milkfat substitute produced by Loders Croklaan (Wormerveer, the Netherlands), is produced by interesterification of vegetable oils in which the component TAGs have been modified to more closely resemble those found in breast milk. This product closely mimics the specific structure and fatty acid composition of human milkfat and resembles breast milk in terms of its nutritional value and high content of palmitic acid at the sn-2 position than other milkfat substitutes. In addition, the use of Betapol in infant formula can lead to improved mineral and fat absorption and less calcium soap formation within the intestinal lumen resulting in softer stools. 

Enzyme-catalyzed reactions are used to produce human mUkfat substitutes for use in infant formulas (46-48). Acidolysis reaction of a mixture of tripalmitin and unsaturated fatty acids using a i -l,3-specific lipase as a biocatalyst afforded TAGs derived entirely from vegetable oils rich in 2-position palmitate with unsaturated fatty acyl groups in the sn- and sn-3 positions (44). These TAGs closely mimic the fatty acid distribution found in human mUkfat, and, when used in infant formula instead of conventional fats, the presence of palmitate in the sn-2 position of the TAGs improved digestibility of the fat and absorption of other important nutrients such as calcium (46, 49). 

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