Zwitterionic headgroups

An attractive class of low toxicity, biodegradable cationic lipids has been derived from the natural PCs, in which the zwitterionic headgroup of the PC is converted into a cation by esterification of the phosphate group (Fig. 3) [16-18]. 

Aqueous solutions of neutral (i.e., nonionic or zwitterionic) surfactants can form micellar assemblies in which a certain number of surfactant molecules aggregate to form an assembly possessing a central core region comprised of long alkyl (or alkylaryl) hydrocarbon chains with their more polar polyethyleneoxide (or zwitterionic) headgroups extending outward and interacting with the bulk water.213... 

Previous studies have shown that surfactant vesicles and tubules can be metallized in a nonselective manner. Since phospholipids with negatively charged headgroups bind metal ions much more strongly than phospholipids with zwitterionic headgroups, Che Pdbind selectively to the negatively charged phospholipids. As a result, selective metallization should occur. 

The initial contact between inhaled partieles and the host will occur at the air-hcpiid interface of the condueting airways and alveoli, where they will become eoated with surfactant. The amount of a surfaetant adsorbed to the surface of particles of quartz or kaolin after mild saline rinsing amounted to the equivalent of a bilayer, in which one monolayer eoats the partiele with their zwitterionic headgroups toward the dust s surface and the ionie phosphorylcholine heads of the second layer orientated toward the aqueous phase (133). These in vitro observations are in keeping with the observations of deposited particles studied by electron microscopy, which show coating with a bilamellar film (2). 

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