Lipid analogs

Niedzinski, E.J., et al. 2000. Gastroprotection of DNA with a synthetic cholic acid analog. Lipids 35 721. 

The technique used for the investigation of specific interaction of phospholipase A2 with substrate monolayers is the fluorescence microscopy. This method is very well known for studying the formation of solid-analogous lipid domains during the main i ase transition in lipid monolayers using a number of different fluorescence microscopy systems [7-9]. Recently it could be shown that fluorescence microcopy is also very suitable to study protein-lipid interactions at monolayers [2-6]. The fluorescence film balance used in all following experiments has been described elsewhere [7]. Materials and experimental procedure are briefly given in the text. A detailed description can be found in the cited papers [7,8]. 

The lipid monolayer is compressed into the phase transition region. This leads to the fonnation of solid-analogous lipid domains in a liquid-analogous matrix (Fig. 4 A). Injection of the labeled phospholipase A2 into the subphase (Fig. 4 B) is followed by specific recognition between the... 

Observation through the fluorescein filter reveals small bright dots after 30 minutes (Fig. 5 F) the protein is starting to aggregate. These bright dots increase in number and size (Fig. 5 F, H, K) imtil, at the end (after about 60 minutes), they have a typical kidney shape (see Fig. 5 L). The monolayer now consists only of almost completely destroyed solid-analogous lipid domains and the protein domains in a mixed matrix of fluid lipid, lysolipid and fatty acid (see Fig. S L, M). 

Luzzati V, Delacroix FI and Gulik A 1996 The micellar cubic phases of lipid-containing systems Analogies with foams, relations with the infinite periodic minimal surfaces, sharpness of the polar/apolar partition J. Physique. II 6 405-18... 

Hydrated bilayers containing one or more lipid components are commonly employed as models for biological membranes. These model systems exhibit a multiplicity of structural phases that are not observed in biological membranes. In the state that is analogous to fluid biological membranes, the liquid crystal or La bilayer phase present above the main bilayer phase transition temperature, Ta, the lipid hydrocarbon chains are conforma-tionally disordered and fluid ( melted ), and the lipids diffuse in the plane of the bilayer. At temperatures well below Ta, hydrated bilayers exist in the gel, or Lp, state in which the mostly all-trans chains are collectively tilted and pack in a regular two-dimensional... 

Heimann and Vogtle [38] synthesized triesters of glycerol with different ether carboxylic acids with a short alkyl chain. They have found that these hydrophilic lipids, in contrast with the fatty acid glycerol triesters, give complex-ation with alkali and alkali earth metal cations in an analogy of crown ethers. 

The formation of nitrosamines in aprotic solvents has applicability to many practical lipophilic systems including foods (particularly bacon), cigarette smoke, cosmetics, and some drugs. The very rapid kinetics of nitrosation reactions in lipid solution indicates that the lipid phase of emulsions or analogous multiphase systems can act as "catalyst" to facilitate nitrosation reactions that may be far slower in purely aqueous media (41, 53, 54). This is apparently true in some cosmetic emulsion systems and may have important applicability to nitrosation reactions in vivo, particularly in the GI tract. In these multiphase systems, the pH of the aqueous phase may be poor for nitrosation in aqueous media (e.g., neutral or alkaline pH) because of the very small concentration of HONO or that can exist at these pH ranges. 

An analogous apparatus to that of Ref. 9 was used to follow the effect of the lipid monolayer on the rate of electron transfer (ET). In this setup [47], an organic phase droplet (1,2-DCE) is continuously expanded into the aqueous phase, and the resulting current transient was monitored in the absence and presence of the adsorbed lipid mono-layer. The rate of ET was decreased as a function of the lipid concentration. 

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