Polymerized vesicles, metallization

The philosophy of membrane-mimetic chemistry may be illustrated by a comparison of plant photosynthesis with sacrificial water photoreduction in artificial systems the process has been mediated by metal-catalyst-coated semiconductor colloids supported on polymerized vesicles (Fig. 4a) [59-64]. 

Metallization of Polymerized Vesicles Formed from Mixtures of Zwitterlonic and Negatively Charged Phospholipids... 

The first approach in using vesicle membranes in nanoparticle synthesis was to polymerize vesicles formed from 9 1 and 1 1 mixtures of 1 and 2 in the presence of Pd(NH3)4Cl2. Palladium ions bound to negatively charged phospholipids in bilayer membranes had been previously demonstrated to serve as catalytic sites for electroless metallization (47). Light scattering revealed that bimodal populations of vesicles were formed both from the 9 1 (31 + 15 nm and 114 + 40 nm) and 1 1 (38 + 13 nm and 109 + 41 nm) mixtures. Exposure of the vesicles to UV radiation (254 nm) resulted in the reaction of 33 % + 6% of the lipid monomer when 10 % of 2 was present and 50% + 4% for vesicles containing 50% 2. The differences in the amount of reaction of monomer are probably due to both ion and pH effects. Non-cross linked polymerized vesicle membranes consist of many individual... 

Polymerization is found assisting the immobilization of carbonic anhydrase on the surface of vesicles. In these examples, polymerization is stabilizing the vesicular structures as well as eliminating the motional properties of lipids i.e., lateral mobility and rotational motion. This explains the poor immobilization of enzyme on polymerized vesicles containing non-polymerizable metal chelating lipid. Detailed studies on the kinetics of enzyme binding with non-polymerizable metal-chelated lipid inserted in polymer constrained environment of polymerized vesicles may provide an insight about the role of polymerization on enzyme immobilization. 

The activity of immobilized carbonic anhydrase on fully polymerized vesicles and no enzyme activity on unpolymerized vesicles clearly leads to the conclusion that cross-linking of the bilayers is a necessary step in the immobilization of enzymes on vesicle surface. Polymerization seemed to help in persevering the architecture and functionalities of organized assemblies. The ligand bound metal ions not only offer... 

Liquid-liquid methods include solvent extraction with immiscible liquid-liquid systems in which a suitable ligand is dissolved in an organic phase and contacted with a metal ion containing an aqueous phase and liquid membranes. Separations can also be achieved with pseudo-phase systems such as micelles, microemulsions, and vesicles. Such separations can be solid-liquid or liquid-liquid and include separations with normal- and reversed-phase silica, and polymeric supports where the mobile phase contains the organized molecular assembly (OMA) of micelles, microemulsions, or vesicles. Separation of metal ions using the pseudo-phase systems is stiU in its infancy and a brief account will be provided here. 

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