Lipids zwitterionic neutral

Fig. 2 Chemical structures of the zwitterionic neutral lipids DOPC (1,2-dioleoyl-.s -glycero-3-phosphatidylcholine) and DOPE (l,2-dioleoyl-S7J-glycero-3-phosphatidylethanolamine) and the cationic lipids DOTAP (l,2-dioleoyl-3-trimethylammonium-propane, a UVL) and MVL5 (a custom-synthesized MVL)...

To better identify the boundaries of the oil-in-water phase and how its characteristics vary with small fluctuations in composition, we extended our analyses of the ternary phase diagram to include more detailed characterization of each phase and a higher resolution map of the oil-water phase. Two lipids— DOPA, an anionic lipid, and lecithin, a zwitterionic neutral lipid—were compared to determine the effect of lipid head group. Five different characterization methods were employed (1) visual classification of the phases, (2) buoyant density, (3) fluorescence quenching, (4) FT-IR, and (5) Cryo-TEM. The rationale for each technique is summarized in Table 15.2. A flow chart for utilizing the information obtained from these methods was developed to objectively evaluate the oil-in-water phase (Fig. 15.5). 

The development of monoalkyl phosphate as a low skin irritating anionic surfactant is accented in a review with 30 references on monoalkyl phosphate salts, including surface-active properties, cutaneous effects, and applications to paste and liquid-type skin cleansers, and also phosphorylation reactions from the viewpoint of industrial production [26]. Amine salts of acrylate ester polymers, which are physiologically acceptable and useful as surfactants, are prepared by transesterification of alkyl acrylate polymers with 4-morpholinethanol or the alkanolamines and fatty alcohols or alkoxylated alkylphenols, and neutralizing with carboxylic or phosphoric acid. The polymer salt was used as an emulsifying agent for oils and waxes [70]. Preparation of pharmaceutical liposomes with surfactants derived from phosphoric acid is described in [279]. Lipid bilayer vesicles comprise an anionic or zwitterionic surfactant which when dispersed in H20 at a temperature above the phase transition temperature is in a micellar phase and a second lipid which is a single-chain fatty acid, fatty acid ester, or fatty alcohol which is in an emulsion phase, and cholesterol or a derivative. 

Cationic lipids are often combined with neutral and zwitterionic lipids in formulations for gene therapy. The most frequent colipids are cholesterol, DOPE and dioleoylphosphatidylcholine (DOPC) (or other PCs) (Fig. 28). These neutral lipids may play a role in transfection by increasing the level of DNA protection against DNases or facilitating the destabilization of the endosomes [35,103]. The optimum cationic lipid/helper lipid stoichiometry varies for the different cationic lipids, nucleic acids, and cells. 

A typical biological membrane is a complex structure composed primarily of lipids and proteins. The major structural components of the bilayer are various lipids. In eukaryotes, the most common type of lipids are phosphatidylcholines, whereas in prokaryotes (such as Escherichia coli), the main lipids are typically phosphatidylethanolamines (1). One example of a typical eukaryotic neutral (zwitterionic) phospholipid is palmitoyl-oleoy 1-phosphatidylcholine (POPC). The molecular structure of POPC is compared to those of dimyristoylphosphatidyl-choline (DMPC) and the negatively charged dimyristoylphosphatidylglycerol (DMPG), commonly used in membrane mimetics, in Fig. 1. 

PC, the trivial name lecithin, is a neutral or zwitterionic phospholipid (Fig. 1). It is the most abundant phospholipid in animal tissues and the main component of nonchloroplast membranes in plants, where it amounts to about 50% of the total lipids. In bacterial membranes, PC is found in small quantities. PC is a useful bilayer component, which has a cylindrical shape and a net neutral charge (1). 

PE (trivial name cephalin ) also has a net neutral charge (Fig. 1). PE is widespread and usually the second most abundant phospholipid in animal and plant membranes. It is also the main lipid component of microbial membranes. In animal tissues, phosphatidylethanolamine may exist in diacyl, aUcylacyl and alkenylacyl forms. Moreover, animal phosphatidylethanolamine usually contains higher levels of arachidonic and docosahex-aenoic acids in comparison with the other zwitterionic phospholipid, PC. The partly methylated derivatives of PE (phos-phatidyl-A -methyl-ethanolamine, phosphatidyl-Af -dimethyl-... 

At physiological pH, the ionophores are ionized with the fat-soluble part of the molecule residing in the lipid bilayer of the membrane and the ionized moiety in the aqueous milieu (4). Binding of the metal ion takes place at the membrane surface As successive ether oxygen atoms from the ionophore bind to the metal, it loses its solvated water molecules, thereby forming a neutral zwitterionic metal-ionophore complex. Transport across the membrane can now take place, and at the opposite surface, the process is reversed to leave the metal cation and the anionic ionophore on the other side of the membrane. The... 

For simplicity of presentation, we assume here membranes containing binary mixtures of acidic and neutral (zwitterionic) lipids. The temporal evolution of the spatially varying charged-lipid compositions on the membrane upper (u) and lower (1) leaflets are linked to the Laplace-Beltrami (LB) operators acting on the corresponding electrochemical potentials through two CH equations (one for each leaflet) each of the form [28] ... 

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