Spacer lipid effect

The effect of lipid ratio on the particle size and morphology of vortexed dispersions (20 mM Tris-HCL pH 8.3) was determined by light scattering and transmission electron microscopy (Table I). As spacer lipid content was increased... 

Polymerized liposomes are being actively investigated for their use in controlled release applications such as drug delivery and biosensors.(24) At present, in order to obtain liposomes which have the release characteristics required for a specific need, the amphiphiles used to construct the liposome as well as the precise mixture of amphiphiles required must be designed and synthesized from start each time. This is a time consuming and expensive process. One of our main objectives in this research is to design a series of liposomes constructed from diacetylenic and short chain spacer lipids with predictable leak rates which could be utilized in controlled release applications. In order to accomplish this goal, it was necessary to characterize both the effect of spacer lipid on microstructure formation properties and to determine the methods that could be used to... 

Figure 6 summarizes the effect of the chain length of the spacer lipid on polymerization. It is observed that the nature of the terminal group on a spacer lipid did not produce any noticeable effect on polymer-... 

Our laboratory mostly works with PEG-cholesterol. It is easily obtained in one step by addition of cholesteryl chloroformate and amino-methoxy-PEG (31). Introduction of a linker between the cholesterol and the PEG part would induce higher membrane fluidity and reduce more efficiently protein interactions as compared to PEG-cholesterol. A diaminobutane spacer was shown to improve significantly the sustained release of calcein from lipoplexes incubated in 30% serum (32). The spacer effect on bicatenar PEG-lipid has not been intensively studied because it can be expected that it would induce less effect on PEG-dioleoyl than on PEG-cholesterol, the lipidic anchor being predominant in the bilayer stabilization (Fig. 2). 

Carrion C, Domingo JC, de Madariaga MA. Preparation of long-circulating immunoliposomes using PEG-cholesterol conjugates effect of the spacer arm between PEG and cholesterol on liposomal characteristics. Chem Phys Lipids 2001 113 97. 

In a second separate approach we proposed a novel family of lipopolyamines (Byk et al., 1997a,b, 1998a,b,c). The novel approach uses, for the first time, solid phase combinatorial chemistry to obtain a variety of geometrically varied mono-functionalized polyamines. The polyamine, the spacer and the lipid moiety of the lipopolyamines were systematically modified, and the effect of these modifications on transfection efficiency was demonstrated both in vitro and in vivo (Byk et al., 1998a) (Figure 15.8). 

Obata Y, Saito S, Takeda N et al (2009) Plasmid DNA-encapsulating liposomes effect of a spacer between the cationic head group and hydrophobic moieties of the lipids on gene expression efficiency. Biochim Biophys Acta-Biomembranes 1788 1148-1158... 

Cholesterol can modify both the hydrophobic attraction between lipid hydrocarbon chains and electrostatic interactions between lipid polar groups. The influence it has on the location of 9HP reflects this dual effect At low temperature, the "spacer" effect of cholesterol allows the ketone to gain access directly to the lipid-water interface. At high temperatures, a more disordered hydrocarbon core favors the solubilization of the guest molecule. 

The interaction effectiveness of biotin with avidin was enhanced by the introduction of a poly(methylene) spacer between the polar head of the lipid and... 

In summary, the dimeric lipids (29a-29h) with low m-value (3-4) and high m-value (20-22) showed exceptional thermal, lipid-packing and cholesterol-association properties. Obviously the introduction of a polymethylene spacer chain at the level of headgroup brought about dramatic effect on the aggregation behavior, membrane organization and lipid packing of 29. 

It is known that a cooperative effect between LA and other natural antioxidants, such as tocopherol (vitamin E) or ascorbic acid, affords the possibility to reduce the formation of reactive oxygen species (ROS), associated with various pathological disorders. Thus triamine spacer as backbone was used to attach Trolox , a water-soluble analogue of vitamin E, and LA, to obtain new analogues 356 which were tested as inhibitors of the microsomal lipid peroxidation. Attachment of LA to the chroman moiety, as in compound 357, is a useful extension of this study <2001JME4300, 2004BMC4835>. 

These observations of the effect of spacers in mixed lipid systems led to the synthesis of an unsymmetrical lipid, in which the alkyl chain at -1 position contained a diacetylenic moiety and sn 2 position contained the spacer chain (see Figure 5). This lipid was dispersed in water to form vesicles, but did not show any polymerization enhancement. This result suggests that symmetric short chain PCs are required for any enhancement in polymerization. 

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