Surfactant lipid content

Many readers may baulk at the hard-core biological content of this Chapter. Fear not. The jargon extends only to a description of where these extraordinary thin-sections have been found in which organism, and in which part of their anatomy. To those unable to digest the jargon, look at the pictures Look again, then compare with the thin-sections of inorganic, surfactant/lipid and polymer systems sho wn in Chapters 2 and 4. 

Natural human surfactant contains 85% phospholipids, 10% neutral lipids, and 5% surfactant proteins or apolipoproteins. Animal surfactants have similar protein and lipid content. Surfactant is synthesized in type II pneumocytes in the alveoli. After secretion, the major... 

The protective effect of the surfactant can be compromised by lyophilization [48], It has been found that, to prevent an increase in particle size, the lipid content of the SLN dispersion should not exceed 5%. Direct contact of lipid particles is decreased in diluted samples. Furthermore, diluted SLN dispersions will also have higher sublimation velocities and a higher specific surface area [49], The addition of cryoprotectors will be necessary to decrease SLN aggregation and to obtain a better redispersion of the dry product. Typical cryoprotective agents are sorbitol, mannose, trehalose, glucose, and polyvinylpyrrolidone. 

Pulmonary surfactant is present in alveolar spaces to lower surface tension and prevent lung collapse during exhalation. This surfactant is a lipoprotein with about 75% of the lipid content being phospholipid. About 75% of this phospholipid is phosphatidyl choline with Qg hydrocarbon chains being most predominant. 

Finally, surfactants play a cmcial role in the study of many biological systems, e.g. biological membranes (Figure 5.15). Biological membranes contain lipid contents that vary from as little as 25% up to 80% by weight. The lipids contained therein are phospholipids, which in water are situated in such a way so that the hydrophilic heads are close to water and the hydrophobic tails are converging so that they can avoid water. Such double phospholipid-layers are present in biological (cell) membranes. 

Cuine, J. F., W N. Charman, C. W Pouton, G. A. Edwards, andC. J. H. Porter(2007). Increasingthe proportional content of surfactant (Cremophor EL) relative to lipid in self-emulsifying lipid-based formulations of Danazol reduces oral bioavailability in beagle ddgj3arm. Res., 24 748-757. 

Components of a photosystem can be inserted selectively into the lipid wall or the inner cavity of the vesicle. For this purpose the lipid and components insoluble in water are dispersed together in aqueous solution by sonification. This leads to an occlusion of water insoluble components within the lipid bilayer. The vesicle membrane is sufficiently stable and impermeable for a number of ions. This allows one to prepare, by gel-filtering, the media of different ionic composition inside and outside the vesicle as shown in Fig. 2b. Such asymmetry of chemical content can be preserved for a rather long time (from several hours to several days). Recently the surfactant molecules with double bonds, which can be polymerized after vesicle preparation, were used for further enhancement of vesicle stability [37-39]. Such polymerized vesicles are stable for several months. 

Nagawa Y, Regen SL (1991) Membrane-disrupting surfactants that are highly selective toward lipid bilayers of varying cholesterol content. J Am Chem Soc 113 7237-7240... 

Contrary to intuitive expectation, organic films on the surface of the sea in the absence of petroleum pollution do not consist of the classically known simple surfactants such as the fatty acids and their esters of planktonic origin. Instead, such films consist for the most part of complex polymeric material with a high degree of hydroxylation, carboxylation and proteinaceous content, with the simple lipids accounting for at most a few percents of ambient sea films and perhaps a little more in compressed natural slicks. There are no qualitative differences in this composition in and out of such slicks, as evidenced by the IR spectral results as well as DOC, DON measurements, etc. Fatty lipids do appear, however, to become more important in natural slicks. 

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