Surfactant lipids

It is important for the theoretical understanding of the formation of various topologies that these aggregates have entropic contributions on the scale of the objects, i.e. on a much larger scale than set by the molecules. These cooperative entropic effects should be included in the overall Helmholtz energy, and they are essential to describe the full phase behaviour. It is believed that the mechanical parameters discussed above kc,k and J0, control the phase behaviour, where it is understood that these quantities may, in principle, depend on the overall surfactant (lipid) concentration, i.e. when the membranes are packed to such a density that they strongly interact. 

A sophisticated respiratory host defence system has evolved to clear airborne particles and potential pathogens in inspired air [106, 143], The system comprises mechanical (i.e. air filtration, cough, sneezing and mucociliary clearance), chemical (antioxidants, antiproteases and surfactant lipids) and immunological defence mechanisms and is tightly regulated to minimise inflammatory reactions [92, 143],... 

Shiffer K, Hawgood S, Duzgunes N, et al. Interactions of the low molecular weight group of surfactant-associated proteins (SP 5-18) with pulmonary surfactant lipids. Biochemistry 1988 27(8) 2689-2695. 

Poelma DL, Zimmermann LJ, Scholten HH, et al. In vivo and in vitro uptake of surfactant lipids by alveolar type II cells and macrophages. Am J Physiol Lung Cell Mol Physiol 2002 283(3) L648-L654. 

KP and v can, in contrast to kp, not be determined via the concentration gradient for binary and ternary mixed micelles, because for the calculation of the Nemstian distribution a constant CMC and an almost constant partial molar volume must be assumed. The calculation of aggregation constants of simple bile salt systems based on Eq. (4) yields similar results (Fig. 8b). Assuming the formation of several concurrent complexes, a brutto stability constant can be calculated. For each application of any tenside, suitable markers have to be found. The completeness of dissolution in the micellar phase is, among other parameters, dependent on the pH value and the ionic strength of the counterions. Therefore, the displacement method should be used, which is not dependent on the chemical solubilization properties of markers. For electrophoretic MACE studies, it is advantageous for the micellar constitution (structure of micelle, type of phase micellar or lamellar) to be known for the relevant range of concentrations (surfactant, lipids). 

It is important to understand the characteristic interactions involved at an interface containing each of the main types of surface-active molecules, i.e., biopolymers (proteins, polysaccharides) and low-molecular-weight surfactants (lipids). But that is not the whole story. In real food systems there are almost always mixed ingredients at the interface. So it is necessary to understand what sorts of mixed interfacial structures are formed, and how they are influenced by the intermolecular interactions. 

The C-terminal domain is a Ca2+-dependent C-type lectin (Chapter 4), while the N-terminal domain is involved in oligomer formation through disulfide bridges. The overall structure is similar to that of the complement protein Clq (Chapter 31).e) Protein D is also collagen-like1 but evidently plays a very different functional role than SP-A. The latter associates with the major surfactant lipids but SP-D does not. It does bind phosphatidyl inositol" and gluco-sylceramide, lipids that are present in small amounts. Perhaps SP-D helps to remove these polar lipids which might interfere with surfactant action.6 Both proteins A and D may also have functions in the immune system.1... 

The methods for preparation of niosomes are similar and as complicated as those used for liposomes. One of the most frequently utilized techniques consists of the hydration of a mixture of the surfactant-lipid at elevated temperature followed by optional size reduction (by sonication, extrusion, homogenization, etc.) to obtain a homogeneous colloidal dispersion and separation of the unentrapped drug [36,40,41,52,55],... 

Hamouda, T., and Baker, J. R., Antimicrobial mechanism of action of surfactant lipid preparations... 

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. 

Stith, I.E. and Das, S.K. (1981). Pulmonary surfactant lipids studies on cholinephosphotransferase in developing guinea pig lung. Indian Biologist 13, 120-8. 

Calfactant (Infasurf) 100/3 Calf lung lavage Surfactant lipids, SP-B (1.7%), SP-C 25 100... 

As a rule, the fluid dispersions (emulsions, foams) are stabilized by adsorption layers of amphiphile molecules. These can be ionic and nonionic surfactants, lipids, proteins, etc. All have the property to lower the value of the surface (or interfacial) tension, o, in accordance with the Gibbs adsorption... 

Silica gel G, impregnated with ammonium sulfate Surfactants, lipids (neonatal respiratory syndrome)... 

Giles (Unilever) Cationic surfactant hydrophilically substituted cationic surfactant lipid An anionic surfactant-free formula providing acceptable cleaning and lathering give wet slippy feel to hair... 

Researchers at Tienzyme, Inc. (B.W. Bogan, principal investigator) in State College, Pennsylvania, are investigating the use of surfactant- or surfactant/lipid-based formulations to enhance the removal of HMW PAHs from creosote- and tar-contaminated soils by bioremediation involving white-rot fungi. 

Soaps and surfactants, lipids, cationic ingredients, and even polymers or polymer association complexes have been used as conditioning ingredients in shampoos and/or conditioning products. Soaps deposit their hydrophobic salts on the hair or bind by metal bridging. Cationic surfactants and polymers attach substantively to hair by ionic bonds enhanced by Van der Waals attractive forces. The substantivity of most polymer association complexes is probably due to their hydrophobic nature, enhanced by Van der Waals forces (entropy) and possibly ionic bonds. 

As previously mentioned many molecules, including surfactants, lipids, and polymers, are amphiphilic, allowing them to possess two very different regions which provide the force required to create unique structures. To minimize the contact between solvent molecules and the lyophobic region of the molecules, nearby amphiphilic molecules are caused to aggregate together forming a stmcture. This structure can be most commonly classified as one of four assemblies bilayer sheet, micelle, vesicle, or a tube. 

Packing and bilayer-micelle transitions in mixed surfactant-lipid systems as studied by solid state NMR... 

This field of sfudy is actually quite old. Interaction and complex formation between natural polymers (proteins) and surfactants (lipids) were recognized early in this century, and much study on mixtures of proteins and synthetic surfactants was carried out in the 1940s and 1950s (1,2). Work on mixtures of synthetic uncharged polymers and ionic surfactants was initiated by Saito in the 1950s and on various (mostly natural) anionic polymers and cationic surfactants by Scott and co-workers at about the same time. For summaries of this early work several reviews are available (3-5). 

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