Lipid position

Haraldsson, G. G. 2007. Chemoenzymatic synthesis of structured lipids positionally labeled with pure fatty acids. In Hou, C. T. (Ed.), Biocatalysis and Biotechnology for Functional Foods and Industrial Products (pp. 55-77). Boca Raton FL CRC Taylor and Francis. 

In the plasma of the newborn pig and infant, 3-0-acyl-D--sphingomyelin has been detected. In this lipid, position 3 of the sphingosine residue was esterified by an additional fatty acid. 

Modified or intermediate liposomes can be obtained by direct mixing of lipids and receptor-modified lipids, by direct reaction of intermediate-modified liposomes with receptor or ligands, or by insertion of modified receptors into the liposomal bilayer. Proteinaceous receptors may be modified with alkyl chains or lipids positioned along the hydrophobic part of the bilayers. Covalent coupling methods have been attempted to bind proteins to functional groups on a liposome surface or to attach a hydrophobic residue covalently to the proteins and allow it to intercalate noncovalently into the bilayer dining or after the formation of the liposome. 

Further addition of fatty acid eventually results in the formation of micelles. Micelles formed from an amphipathic lipid in water position the hydrophobic tails in the center of the lipid aggregation with the polar head groups facing outward. Amphipathic molecules that form micelles are characterized by a unique critical micelle concentration, or CMC. Below the CMC, individual lipid molecules predominate. Nearly all the lipid added above the CMC, however, spontaneously forms micelles. Micelles are the preferred form of aggregation in water for detergents and soaps. Some typical CMC values are listed in Figure 9.3. 

Death from overdose of barbiturates may occur and is more likely when more than 10 times the hypnotic dose is ingested. The barbiturates with high lipid solubility and short half-lives are the most toxic. Thus the lethal dose of phenobarbital is 6—10 g, whereas that of secobarbital, pentobarbital, or amo-barbital is 2-3 g. Symptoms of barbiturate poisoning include CNS depression, coma, depressed reflex activity, a positive Babinski reflex, contracted pupils (with hypoxia there may be paralytic dilation), altered respiration, hypothermia, depressed cardiac function, hypotension, shock, pulmonary complications, and renal failure. 

In the pharmaceutical industry, GA is used in pharmaceutical preparations and as a carrier of drugs since it is considered a physiologically harmless substance. Additionally, recent studies have highlighted GA antioxidant properties (Trommer Neubert, 2005 Ali Al Moundhri, 2006 Hinson et al., 2004), its role in the metabolism of lipids (Tiss et al., 2001, Evans et al., 1992), its positive results when being used in treatments for several degenerative diseases such as kidney failure (Matsumoto et al., 2006 Bliss et al., 1996 Ali et al., 2008), cardiovascular (Glover et al., 2009) and gastrointestinal (Wapnir et al., 2008 Rehman et al, 2003). 

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