Complex lipids, chemistry

Due to the complexity of the transfection pathway, no general schemes have evolved for correlating cationic lipid chemistry with transfection activity. A useful approach for designing and optimizing the cationic lipid vectors, as well as for... 

Improvements in SIMS and FAB which lead to more intense ion beams are highly desireable because that will permit the information to be obtained for smaller samples and for lower abundance constituents in complex mixtures such as surfactants. Moreover, consecutive activation steps (MS/MS/MS) should be important in investigations of mixtures of complex lipids and related materials. Here one step of collisional activation is necessary to liberate the fatty acid carboxylate and a second step is required to activate the anions. These experiments also require intense ion beams. It is our hope that the analytical possibilities raised by the chemistry discusses here will stimulate further research to improve FAB and SIMS. 

Silver-ion TLC is the modification with the most important impact on the development of lipid chemistry and has been of immense importance for the understanding of lipid structure. It is used to resolve the molecular species of a single lipid class. The separation is based on the ability of unsaturated fatty acid moieties in lipid molecules to form weak reversible charge-transfer complexes with silver ions. The complexation includes the formation of a a-type bond between the occupied 2p orbitals of the oleflnic double bond in the fatty acid (FA) moiety and the free 5s and 5p orbitals of the silver ion, and a (probably weaker) rr-acceptor backbond between the occupied 4d orbitals of the silver ion and the free antibonding Ipv orbitals of the olefinic bond. Thus, Ag TLC separates lipid classes into molecular types depending on the number, configuration, and, occasionally, the position of the double bond in the fatty acid moieties. 

D.E.Minnikin, Lipids Complex Lipids, Their Chemistry, Biosynthesis and Roles. In The Biology of Mycobacteria C. Ratledge, J. Stanford, Eds. Academic Press London, 1982 pp 95-184. 

The lipids are among the most important components of human diet and occur widely in nature. However, it is the biochemical role of lipids as the basic components of various cellular membranes and the lipid-protein complexes (lipoproteins) that bring them into the focus of highly important scientific activities. Major clinical interest has concentrated on blood lipid chemistry as related to atherosclerosis, lipid storage diseases, diabetes, and other metabolic conditions. 

The chemistry of complex lipids is dominated by regioselective hydrolysis reactions of (1) the glyceryl fatty acid esters and (2) phosphate diesters. Both types of reactions are routinely performed with the corresponding esterases. A large variety of lipid active transferase enzymes is also commercially available. Phospholipases Aj, A, C, and D, for example, split any of the four ester bonds of a phospholipid regioselectively. The product without a fatty acid side chain at C2 of glycerol is called a lysophospholipid. Lecithin-cholesterol-acyltransferase transfers the fatty acid at C2, often linoleic acid, to the OH group at C3 of cho-... 

The vehicle format we have used to produce aquasomes is the complex particulate multicomponent system. In general, complex particulate delivery systems are assemblies of simple polymers, complex lipid mixtures or ceramic materials that tend to measure individually between 30 and 500 nm in diameter. Being solid or glassy particles dispersed in an aqueous environment, they exhibit the physical properties of colloids their mechanism of action is controlled by their surface chemistry. They may deliver agents through a combination of specific targeting, molecular shielding, and slow release processes. 

Murphy, R.C. (2015) Tandem Mass Spectrometry of Lipids Molecular analysis of complex lipids. Royal Society of Chemistry, Cambridge, UK. pp 280. 

LaLonde, J.M., Levenson, M.A., Roe,J.J., Bemlohr, D.A. and Banaszak, L.J. (1994) Adipocyte lipid-binding protein complexed with arachidonic acid titration calorimetry and X-ray crystallographic studies. Journal of Biological Chemistry 269, 25339-25347. 

At physiological pH, ONOO- protonates to peroxynitrous acid (ONOOH) which disappears within a few seconds, the end product being largely nitrate. The chemistry of peroxynitrite/peroxynitrous acid is extremely complex, although addition of ONOO to cells and tissues leads to oxidation and nitration of proteins, DNA and lipids with a reactivity that is comparable to that of hydroxyl radicals. 

The previous result is an important one. It indicates that there can be yet another fruitful route to describe lipid bilayers. The idea is to consider the conformational properties of a probe molecule, and then replace all the other molecules by an external potential field (see Figure 11). This external potential may be called the mean-field or self-consistent potential, as it represents the mean behaviour of all molecules self-consistently. There are mean-field theories in many branches of science, for example (quantum) physics, physical chemistry, etc. Very often mean-field theories simplify the system to such an extent that structural as well as thermodynamic properties can be found analytically. This means that there is no need to use a computer. However, the lipid membrane problem is so complicated that the help of the computer is still needed. The method has been refined over the years to a detailed and complex framework, whose results correspond closely with those of MD simulations. The computer time needed for these calculations is however an order of 105 times less (this estimate is certainly too small when SCF calculations are compared with massive MD simulations in which up to 1000 lipids are considered). Indeed, the calculations can be done on a desktop PC with typical... 

By the second half of the nineteenth century German chemists had established a dominant position in analytical and synthetic organic chemistry. Various simple sugars and aminoacids were being isolated and characterized, as well as more complex plant products. Studies on the composition of blood and the properties of hemoglobin were also well under way. The composition of lipid-rich components and the order of the different units within complex macromolecules, such as proteins and nucleic acids, could not however be resolved by techniques then available. 

Much of industrial chemistry takes place in organic solvents, or involves apolar compounds. Biocatalysis, in contrast, typically involves aqueous environments. Nevertheless, enzymes and microorganisms do in fact encounter apolar environments in Nature. Every cell is surrounded by at least one cell membrane, and more complex eukaryotic cells contain large amounts of intracellular membrane systems. These membranes consist of lipid bilayers into which many proteins are inserted present estimates, based on genomic information, are that about one-third of all proteins are membrane proteins, many of which are so-called intrinsic proteins that are intimately threaded through the apolar bilayer. These proteins are essentially dissolved in, and function partly within, an apolar phase. 

Of the four major classes of biochemicals (carbohydrates, proteins, nucleic acids and lipids), experiments have shown that the first three classes could have arisen through prebiotic chemistry. Although the biosynthesis of many natural products can be traced back to acetate (e.g. fatty acids, terpenes and polyketide biosynthesis) or amino acids (e.g. alkaloid biosynthesis), there are many whose biosynthetic origins are either obscure or result from a complex combination of pathways (Fig. 2). 

Carbohydrates are relevant in medicinal chemistry. The outdated notion that carbohydrates serve only as energy sources in animals and structural materials in plants is no longer tenable. Complex carbohydrates are biochemically important. Carbohydrates, when joined via glycosidic linkages to either proteins or lipids (to produce glycoproteins or... 

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