Lipid classes, definition

In contrast, no significant difference in the degree of lymphatic absorption of halofantrine was detected following administration in TG or in FA-MG blend [88]. Hence, definite conclusions regarding the effect of lipid class utilized on the extent of lymphatic transport cannot yet be drawn. 

Lecithin is a polar lipid, the definition being that it is a lipid that is insoluble in acetone. It is one of a whole class of phospholipids, which tend to be found in the membranes of animals and also in plants. 

Unfortunately, not all molecular species are detected with equal efficiency by MS. The detection of an individual phospholipids is dependent both upon radyl chain saturation and length with a greater intensity of response being determined for more unsaturated species, but a lower response being found as the chain length increased. In addition the detection of the different lipid classes is affected by solvent since this can alter the nature of the adduct formation and thus simplify or make more complex the spectra. The CID fragmentation of lipids in most cases permits the definitive identification of individual species. 

Analyses of serum lipids in NPD are available in relatively few cases. From the reported data it appears that, in general, there are no specific abnormalities of serum lipids, and in particular no increase, absolute or relative, of serum sphingomyelins. Mild and often transient hyperlipidemias have been described which usually involve all lipid classes to a similar degree. In several patients of Crocker and Farber (1958) the degree of hyperlipidemia paralleled the increase in tissue lipids. It is likely that the mild hyperlipidemia in NPD represents a non-specific abnormality, but a definite answer to these questions has to await more precise information on the regulatory mechanisms of serum lipids. 

Although elution time from a LC separation provides valuable information for a particular species, definitive identification of the lipid species has to be performed based on its product-ion mass spectrum. For those researchers who are using LC-MS for identification and quantification of lipid species, familiar with the fragmentation patterns of lipid classes, therefore deriving the product-ion mass spectra of individual lipid species, is very important although a few databases and/or libraries (see Chapter 5) can be used to aid the identification. Resolving complex biological lipids into a... 

For additional information on the definition and the nomenclature of lipid classes, see Gunstone and HerslOe, 1992... 

By definition POV is the number of miliequivalents of active oxygen per kilogram of sample" , or in some cases the number of micrograms of active oxygen in one gram of sample, capable of oxidizing iodide to iodine" °°. Many of the methods described in Section V for determination of hydroperoxide classes or individual compounds can also be applied for determination of POV, as total hydroperoxides. The iodometric determination of hydroperoxides in lipids and proteins has been reviewed . 

Lipids are naturally occurring organic molecules, isolated from animal or plant cells by extraction with nonpolar organic solvents. This definition defines lipids in terms of a physical property (solubility) and differs from structural definitions used for proteins or carbohydrates. Not surprisingly, lipids are highly varied in their structure from the medicinal chemistry perspective, there are five classes of lipids ... 

Nonreceptor-Mediated Drug Action. At least one important class of drugs, the general anesthetics, has been assumed not to owe its therapeutic activities to a specific receptor process. Anesthetic potency shows an excellent linear correlation with partition coefficient and this has been extrapolated to a definition of action at a lipid site. The phospholipids of cell membranes, particularly nerve cells, have been considered as principal targets for general anesthetic action. It has been hypothesized... 

Lipids can be defined as all the substances produced by organisms that are effectively insoluble in water but extractable by solvents that dissolve fats (e.g. chloroform, hexane, toluene and acetone). This broad definition is suitable for our purposes and encompasses a wide variety of compound classes, including photosynthetic... 

The term lipids is defined as those organic compounds that are insoluble in water, soluble in organic solvents (e.g., chloroform, ether), contain hydrocarbon groups as primary parts of the molecule, and are present in or derived from living organisms. Compound classes covered in this definition include fatty acids (FA), acylglycerols, FA esters (e.g., waxes), and isoprenoid hydrocarbons. Other compounds also included are often considered as belonging to different classes, such as carotenoids, sterols, and the vitamins A, D, E, and K. 

A contribution to the understanding of lipoprotein metabolism would be the definition of the metabolic role of the lysolecithin-rich d 1.21 lipoprotein. This protein-phospholipid complex may simply represent a degradation product of the high-density lipoprotein after removal of the other lipid moieties. On the other hand, it could be considered as a newly synthesized product from the liver on its way to further lipidation to form a more complete class of lipoproteins. Its possible identity with the apolipoprotein described by Roheim and Eder (1961 Roheim et al., 1964) remains to be established. 

With the establishment of techniques for isolation and characterization of lipoprotein proteins, further definition of the lipoprotein changes in biliary obstruction ought to be possible. Furman et al. (1961) have exposed in vitro sera from subjects with biliary obstruction to sonic forces. Cholesterol and phospholipid contents of the LDL class diminished while a comparable increase of these lipids in the HDL class occurred. These data were interpreted to indicate that in obstructive jaundice serum LDL and HDL are to a certain extent associated. 

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