Hydrophilic spacer

Elbert R, Laschewsky A and Ringsdorf H 1985 Hydrophilic spacer groups in polymerizable lipids— formation of biomembrane models from bulk polymerized lipids J. Am. Ohem. Soc. 107 4134-41... 

Schneider J, Erdelen C, Ringsdorf H and Rabolt J F 1989 Structural studies of polymers with hydrophilic spacer groups. 2. Infrared-spectroscopy of Langmuir-Blodgett multilayers of polymers with fluorocarbon side-chains at ambient and elevated temperatures Macromolecules 22 3475-80... 

Hydrophilic spacer groups may be introduced into a polymer through the side chain, the main chain, or both. Films can be prepared using different values of monomer feed (62). 

A novel polymerized vesicular system for controlled release, which contains a cyclic a-alkoxyacrylate as the polymerizable group on the amphiphilic structure, has been developed. These lipids can be easily polymerized through a free radical process. It has been shown that polymerization improves the stabilities of the synthetic vesicles. In the aqueous system the cyclic acrylate group, which connects the polymerized chain and the amphiphilic structure, can be slowly hydrolyzed to separate the polymer chain and the vesicular system and generate a water-soluble biodegradable polymer. Furthermore, in order to retain the fluidity and to prepare the polymerized vesicles directly from prev lymerized lipids, a hydrophilic spacer has been introduced. 

Figure 7.10 An NHS-PEG-maleimide compound can be used to functionalize dendrimers to provide a hydrophilic spacer terminating in thiol-reactive groups. Thiol-containing proteins then can be conjugated to this reactive intermediate to form covalent thioether bonds.

Figure 18.5 The modification of an APTS-modified surface containing amines with bis-NHS-PEG5 yields hydrophilic spacers containing terminal NHS esters for coupling proteins.

Modification of dextran polymers with 1,4-butanediol diglycidyl ether results in ether derivatives of the dextran hydroxyl groups, which then contain hydrophilic spacers with terminal epoxy functions (Figure 25.16). 

Capture oligonucleotide probes complementary to the mRNAs are arrayed onto a glass substrate with immobilization via a 3 terminal amino group. Since the mRNA is 5 to the polypeptide, capture results in orientation of the polypephde away from the surface (Figure 6.25, Step D). The capture probes are tethered to the substrate indirectly via a hydrophilic spacer arm composed of hexaethylene oxide-phosphodiester units that terminate with the 3 amino group. 

Fig. 13. Schematic representation of the influence of the hydrophilic spacer on the area occupied by the lipids in the monolayer. High mobility of the spacer requires large areas in the fluid phase (left). Reduced mobility of the spacer results in a decrease of the area occupied (right) [172]...

Wilchek [51] has described poly-DL-alanine poly-L-lysine agarose derivatives. These gels offer the advantage of introducing a hydrophilic spacer and thus reducing non-specific hydrophobic interactions with the spacer. 

Two methods for the covalent immobilization of single-stranded DNA onto fused silica optical fibres using various linkers for the development of biosensors were reported by Krull and co-workers [22]. One method involved a hydrophobic and the other a hydrophilic spacer arm and it was determined which linker would provide the best immobilization efficiency, hybridization kinetics, and minimal non-specific adsorption to the surface. 

The final class of important synthetic lipids are those with a polymerizable substituent. A significant concept present is the introduction of a hydrophilic spacer group between the hydrophobic core and the polymerizable group. Only in polymers made of spacer lipids does the polymer chain remain flexible enough to decouple its movements from those of the membrane in order to... 

Prepolymerized lipids form vesicles only if the disentanglement of the polymer main chain ( = hack hone) and the membrane forming side-chains is simplified hy a hydrophilic spacer between them . Efficient decouplings of the motions of the polymeric chain and the polymeric bilayer are thus achieved and stable liposomes with diameters of around 500 nm were formed upon ultrasonication (Figure 4.28a). Their bilayer showed a well-defined melting behaviour in DSC. The ionene polymer with C12, C16 and C20 intermediate chains also produced vesicles upon sonication (Figure 4.28b). Here, the amphiphilic main chain is obviously so simple that ordering to form membranes produces no problems whatsoever . ... 

Figure 4.28 a) Disentanglement of the polymer main chain from the membrane surface by hydrophilic spacers, often ethylene glycol oligomers, is the best means to synkinetize vesicles from amphiphilic polymers. Ordering of the amphiphiles must not be disturbed by their covalent connections, b) Folding of the ionene polymer spontaneously yields monolayer vesicle membranes. ... 

Bisepoxirans activations allows the coupling of ligands containing —OH, —NH2, and —SH groups with agarose matrix. Here, the ligands are provided automatically with a hydrophilic spacer arm. 

Apart from hpid molecules, the molecules that are most commonly employed for the fabrication of biomimetic membranes are hydrophilic spacers and thi-olipids. Hydrophihc spacers consist of a hydrophihc chain (e.g., a polyethyleneoxy or oligopeptide chain) terminated at one end with an anchor group for tethering to a support and, at the other end, with a hydrophihc functional group (e.g., a... 

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