Lipid fraction

Phosphatidylcholine is an important component of cell membranes but cell mem branes are more than simply lipid bilayers Although their composition varies with their source a typical membrane contains about equal amounts of lipid and protein and the amount of cholesterol m the lipid fraction can approximate that of phosphatidylcholine The lipid fraction is responsible for the structure of the membrane Phosphatidyl choline provides the bilayer that is the barrier between what is inside the cell and what IS outside Cholesterol intermingles with the phosphatidylcholine to confer an extra measure of rigidity to the membrane... 

Research in physiology carried out in the 1930s established that the lipid fraction of semen contains small amounts of substances that exert powerful effects on smooth mus cle Sheep prostate glands proved to be a convenient source of this material and yielded a mixture of structurally related substances referred to collectively as prostaglandins We now know that prostaglandins are present m almost all animal tissues where they carry out a variety of regulatory functions... 

The lipid fraction is responsible for the structure of the membrane. Phosphatidylcholine provides the bilayer that is the banier between what is inside the cell and what is outside. Cholesterol intermingles with the phosphatidylcholine to confer an extra measure of r-igidity to the membrane. 

No discussion of the use of biotransfarmation in lipid chemistry would be complete without some mention of chemical transformation relating to fatty adds. Fatty adds are a major component of the lipid fraction of organisms. They are mainly found as components of triglycerides and phospholipids, although they may occur in smaller quantities as free fatty adds or as esters of other moieties. Fatty adds, either as free adds or as esters, are valuable commodities in the food and cosmetics industries. They may also serve as precursors of a variety of other compounds. 

Figure 38, Patterns obtained from the extract of 10 fd of serum for lipid fraction by thin-layer chromatography. In sequence, starting from the bottom, phospholipids, pee cholesterol, cholesterol aniline as an internal standard, triglycerides, and cholesterol esters. The free fatty acids occur between cholesterol and the internal standard and are only barely visible in the print, on the extreme right. They are readily visible, normally, to the eye.

Chedid, A. Haux, P. and Natelson, S. Use of thin layer chromatography on silica gel for serum lipid fractionation and measurement in the routine clinical laboratory. Clin. Chem. (1972), 13, 384 - 390. 

Isotachis lyallii Mitt, is a liverwort that occurs on both the north and south islands of New Zealand. A study of the lipid fraction of this species collected from both islands revealed different secondary metabolite profiles involving sesquiterpenes and aromatic esters (Asakawa et al., 1997). The sesquiterpene array consisted of... 

Those authors also demonstrated that neither sexual stage nor age of plant had any effect on the qualitative composition of the lipid fractions. They did comment, however, on the possibility that the secondary chemical output of plants at these different sites might reflect local environmental conditions, especially considering that the distance between the sites at Castelluccio and Brucoli is only a few kilometers. They pointed to the work of Howard et al. (1980), who had demonstrated such effects on the chemical content of two species of Laurencia in California over... 

After the extrachon of total lipids from four different genotypes of flax seed (Linum usitassimum) differing markedly in their acyl composihon, PTLC was used for the isolahon of different lipid classes in the neutral lipid frachon [69]. Application of planar chromatographic methods, including PTLC, in the separahon of food lipids has been reviewed with 40 references by Olsson [70]. The polar lipid fraction of niger seed (Guizotia abyssinica Cass.) collected from different regions of Ethiopia could be separated by PTLC on silica gel [71]. 

After the extraction of lipid and nonlipid components from the leaves of mandarin orange Citrus reticulata, the lipid fraction was further separated by PTLC to determine different lipid classes that affect the chemical deterrence of C. reticulata to the leaf cutting ecat Acromyrmex octopinosus. These lipids seem to be less attractive to the ants [81a]. The metabolism of palmitate in the peripheral nerves of normal and Trembler mice was studied, and the polar lipid fraction purified by PTLC was used to determine the fatty acid composition. It was found that the fatty acid composition of the polar fraction was abnormal, correlating with the decreased overall palmitate elongation and severely decreased synthesis of saturated long-chain fatty acids (in mutant nerves) [81b]. 

At present, the activation of the extrinsic coagulation system is considered to be of more importance in the initiation of DIC than the activation of the contact system (LI2, Cl 3). The activation of the extrinsic system starts with the release of tissue factor (TF) from endothelial cells. TF is a macromolecule, composed of a protein and a lipid fraction, that is synthesized by endothelial cells and monocytes. TF... 

There has not been found any substantial difference between the effects of irradiation on the lipid fraction of complex foods and that on model systems analogous to to fats. The autooxidation products of either natural fats or of model systems on irradiation are the same as those present in oxidized fats that... 

Additional hypotheses concerning prostaglandin biosynthesis in P. homomalla resulted from isolation of 11R-HETE (76) from the polar lipid fraction [95]. Apparently, 11R-HETE (76) is also a minor product of incubations of arachidonic acid with acetone powder preparations of P. homomalla [95], In this alternate hypothesis (Scheme 8), an 11-hydroxy or 11-hydroperoxy-8,9-allene oxide intermediate is formed from a sequence of oxidations at C8 and Cll. Opening of the allene oxide to a transient C8 earboeation induces eycli-zation with a consequent addition of water to C15. This proposed pathway leads initially to formation of PGE2 (16 or 38), which following acetylation, elimination of acetic acid from Cl 1-12, and esterification, forms the observed major natural product in the coral, 15-acetoxy methyl PGA2 (36 or 54). Notably, if... 

The ORAC assay proposed by Ou and others (2001) is limited to hydrophilic antioxidants because of the aqueous environment of the assay. However, lipophilic antioxidants play a critical role in biological defense systems. Huang and others (2002) expanded the assay to the lipidic fraction by introducing a randomly methylated 13-cyclodextrin (RMCD) as a water-solubility enhancer for lipophilic antioxidants. Various kinds of foods, including fruit juices and drinks, fruits, vegetables, nuts, and dried fruits, have been evaluated with this method (Zhou and Yu 2006 Wu and others 2004 Kevers and others 2007 Wang and Ballington 2007 Almeida and others 2008 Mullen and others 2007). 

Although the 100% extraction rate ensures a bigger yield, wholemeal is not particularly popular with millers as a stronger grist is needed. In addition, its shelf life is only three months (cf. a year for white flour). The reduction in shelf life is supposed to be caused by oxidation of the lipid fraction that is absent from white flour. Furthermore, wholemeal flour must be kept apart from white flour less that is contaminated. 

In about 1936, sialic acid was discovered by Blix, who found it to be a component of submaxillary-gland proteins, and who described many of its properties. However, little notice was taken of this work at the time it was published. In 1941, Klenk, who was working on glycolipids of the brain, described a compound, later shown to be a methyl glycoside of sialic acid, that had been obtained by treatment of a lipid fraction with 5% methanolic hydrogen chloride at 105°. In 1954, Klenk and Faillard reported the first isolation of pure N-acetyl-neuraminic acid from animal sources. 

It is unknown which compounds are involved in Liolaemus communication. However, information available from the chemical composition of the lipidic fraction of the precloacal secretions suggests that individuals, populations and species can be discriminated by the chemical profile of these secretions (Escobar, Escobar, Labra and Niemeyer 2003 Escobar, Labra and Niemeyer 2001). This, in addition to probable chemical differences in the other sources of chemosignals, may allow individual, population and species recognition (Labra et al. 2001). Based on the individual variation observed in the composition of the secretions of L. bellii (Escobar et al. 2001), it is likely that lizards can achieve self-recognition, and also that they can extract detailed information about sender characteristics, as we have seen for L. monticola (Labra 2006). 

One advance in the area of LLE is the use of solid supports that facilitate the partitioning of the analyte(s) of interest. LLE extraction methods involving nonpolar matrices often suffer from the formation of emulsions, and using the solid support is a possible solution. In one study, polychlorinated biphenyls, dioxins, and furans were extracted from the lipid fraction of human blood plasma [32], using diatomaceous earth as the solid support. Long glass columns (30 cm) were packed with several layers of Chem-Elut (a Varian product) and sodium chloride. The plasma samples were diluted with water and ethanol and passed over the columns. A mixture of isopropanol and hexane (2 3) was passed over the column and the LLE was performed. It can be concluded that the LLE with the solid support is easier to perform and can be applied to other lipid heavy matrices such as milk [32]. 

According to Chandler (C4), there is no circadian variation, but one should keep in mind that the distribution of Lp(a) over the different lipid fractions after a meal differs from the distribution in fasting serum samples (B11, E8). 

CAROTENOID COMPOSITION (PERCENTAGE OF TOTAL S.E.) OF FULLY FORMED FEATHERS, BLOOD AND UNKERATINIZED LIPID FRACTIONS FROM MATURING FEATHER FOLLICLES IN FOUR PASSERINES THAT DISPLAY YELLOW PLUMAGE COLOURATION... 

In general, our studies with cytochrome P-450-dependent metabolism have emphasized the similarity of the hepatic MFO system in marine fish to that found in mammals. Thus, in the little skate (Raja erinaoea), a marine elasmobranch, enzyme activity is localized in the microsomal fraction, requires NADPH and molecular oxygen for maximum activity, and can be inhibited with CO (1, 2). Moreover, when hepatic microsomes from the little skate were solubilized and separated into cytochrome P-450, NADPH-cytochrome P-450 reductase, and lipid fractions, all three fractions were required for maximal MFO activity in the reconstituted system (3). We have also found, as have others, that the administration of polycyclic hydrocarbons (3-methylcholanthrene, 1,2,3,4-dibenzanthracene [DBA]), 2,3,7,8-tetrachlorodibenzo-p-dioxin... 

Aliphatic hydrocarbons, a diverse suite of compounds, are an important lipid fraction which is either natural (i. e., from photosynthesis by marine biota inhabiting the surface waters or by terrestrial vascular plants) or anthropogenic (i. e., of petroleum origin from land runoff, and/or industrial inputs). Aliphatic hydrocarbons have been studied and characterized from various environmental multimedia [1,53-56,99-109]. 

For parallel permeation pathways within a single layer of such a laminate, the total permeability may be calculated as the sum of the permeabilities [49], For example, when assuming that permeation may occur through both a lipid fraction and a protein fraction of the stratum corneum, the total permeability is calculated according to Eq. 34 ... 

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