Polymerized lipid, molecular structure

We report here on the structure and gas transport properties of asymmetric membranes created by the Langmuir-Blodgett deposition of ultra-thin polymeric lipid films on porous supports. Transmission and grazing angle FTIR spectroscopy provide a measure of the level of molecular order in the n-alkyl side-chains of the polymeric lipid. The level of orientational order was monitored as a function of the temperature. Gas permeation studies as a function of membrane temperature are correlated to the FTIR results. 

Materials and Film Preparation. The molecular structure of the polymerized lipid referred to as CO-1.5 is shown in Figure 1. The material is a co-polymer of a double 18-carbon alkyl chain lipid with a side-group spacer and five main-chain spacer groups. The purpose of the spacer chains is to allow more free volume for the lipid chains to orientationally order normal to the polymer backbone. The lipid chain contains an amide, and the main-chain spacer groups contain tertiary amines. The polymer was synthesized following the general procedures given by Laschewsky et al. (10). 

Sil-ODA has been developed to address this question.The ODA phase does not make lipid membrane structures in an aqueous system, but it possesses similar functions, such as side-chain ordering and phase transition behavior between ordered and disordered states. However, the resultant selectivity in HPLC often excelled, better than expected. This is due to a sort of a side effect and, then, it may be called a polymeric effect, which promotes multiple interactions to increase the selectivity. Molecular ordering of functional groups particularly enhances it. 

While most vesicles are formed from double-tail amphiphiles such as lipids, they can also be made from some single chain fatty acids [73], surfactant-cosurfactant mixtures [71], and bola (two-headed) amphiphiles [74]. In addition to the more common spherical shells, tubular vesicles have been observed in DMPC-alcohol mixtures [70]. Polymerizable lipids allow photo- or chemical polymerization that can sometimes stabilize the vesicle [65] however, the structural change in the bilayer on polymerization can cause giant vesicles to bud into smaller shells [76]. Multivesicular liposomes are collections of hundreds of bilayer enclosed water-filled compartments that are suitable for localized drug delivery [77]. The structures of these water-in-water vesicles resemble those of foams (see Section XIV-7) with the polyhedral structure persisting down to molecular dimensions as shown in Fig. XV-11. 

Even if membranous vesicles were commonplace on the early Earth and had sufficient permeability to permit nutrient transport to occur, these structures would be virtually impermeable to larger polymeric molecules that were necessarily incorporated into molecular systems on the pathway to cellular life. The encapsulation of macromolecules in lipid vesicles has been demonstrated by hydration-dehydration cycles that simulate an evaporating lagoon [53] or by freeze-thaw cycles [54]. Molecules as large as DNA can be captured by such processes. For instance, when a dispersion of DNA and fatty acid vesicles is dried, the vesicles fuse to form a multilamellar sandwich structure with... 

This book describes the science and practice behind the materials in foods that impart their desirable properties. The first part of the book describes those physicochemical aspects that intervene in the organization of food components from the molecular level to actual products and methods used to probe into foods at different length scales. The second part explains how food structures are assembled during processing in order to achieve desirable and recognizable properties. Processed foods are mostly metastable structures in which water, air, and lipids are immobilized as dispersed phases within a polymeric matrix of proteins, polysaccharides, or a fat crystal network. The last section of the book presents specific examples of how structures of familiar products are obtained by processing and describe some new developments. 

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