Enhanced cation transfer

More recently, Manzanares et al. [17] presented additional experimental evidence of the enhanced cation transfer across a hemispherical water-1,2-DCE interface covered with DSPC by using a syringe experimental set up described elsewhere [9,28]. Figure 7 shows the cyclic voltammograms measured in the cell [17],... 

The theory presented above accounts for the electrostatic effects on the apparent rate constant for ion transfer by relating the observed changes in to changes in c"(0), or equivalently to 0(0). In the following, we present the simulated electrical potential distributions and the corresponding enhancement factors for a cation transferring from the aqueous phase across the water-l,2-DCE interface (s" = 78.39, s° = 10.36). The rela-... 

A theoretical approach based on the electrical double layer correction has been proposed to explain the observed enhancement of the rate of ion transfer across zwitter-ionic phospholipid monolayers at ITIES [17]. If the orientation of the headgroups is such that the phosphonic group remains closer to the ITIES than the ammonium groups, the local concentration of cations is increased at the ITIES and hence the current observed due to cation transfer is larger than in the absence of phospholipids at the interface. This enhancement is evaluated from the solution of the PB equation, and calculations have been carried out for the conditions of the experiments presented in the literature. The theoretical results turn out to be in good agreement with those experimental studies, thus showing the importance of the electrostatic correction on the rate of ion transfer across an ITIES with adsorbed phospholipids. 

Schwartz, B., Ivanov, M.-A., Pitard, B., Escriou, V., Rangara, R., Byk, G. et al. (1999) Synthetic DNA-compacting peptides derived from human sequence enhance cationic lipid-mediated gene transfer in vitro and in vivo. Gene Ther., 6,282-292. 

Cheung CY, Murthy N, Stayton PS, Hoffman AS. A pH-sensitive polymer that enhances cationic lipid-mediated gene transfer. Bioconjung Chem 2001, 12, 906-910. 

Poly(e-caprolactone) is another practically important polyester formed by ionic polymerization of the cyclic ester. Cationic polymerization requires relatively high temperatures this enhances proton transfer and decreases the molecular weight, whereas anionic polymerization provides living systems. 

Knowledge of how aluminum chloride oxidizes aromatics to cation radicals is practically non-existent. At one time it seemed that a nitro compound was a necessary co-acceptor (Buck et al., 1960) and that, whereas with mononuclear alkylaromatics, the Lewis acid-nitro compound pair formed only charge transfer complexes (Brown and Grayson, 1953), complete electron transfer occurred with more easily oxidized aromatics. But, cation-radical formation from perylene, anthracene, and chrysene was found to occur in carbon disulfide, chloroform, and benzene solutions, too (Rooney and Pink, 1961) and even occurs on warming anthracene and naphthacene with solid aluminum chloride (Sato and Aoyama, 1973). There is no doubt that a nitro compound enhances electron transfer, however (Sullivan and Norman, 1972). Cation radical formation in AlCl3-nitromethane has been estimated as approximately 100% as compared with 1% in sulfuric acid oxidation of dialkoxybenzenes (Forbes and Sullivan, 1966). Unfortunately, aluminum halide salts have not been isolated and, therefore, even the beginnings of analytical data have yet to be collected. There is no definite knowledge of either the nature of the counter ion or the fate of the electrons in these cation-radical formations. 

Other areas of interest include stabilization of noncommon oxidation states, solvent extraction of cations, transfer of cations through membranes, isotopic separation, detoxification of harmful and radioactive metals, metal recovery, metal trace analysis, ion chromatography on polymer-supported cryptands, and chromo- and fluoro-ionophores. More organic-chemistry-orientated applications can be mentioned, including enhancement of metal salt solubility in organic solvents, anion activation, phase-transfer catalysis, and anionic polymerization. Many of these applications are covered in other articles in this encyclopedia as well as in the literature. 

Cheung, C. Y., N. Murthy, P. S. Stayton and A. S. Hoffman, 2001, A pH-sensitive polymer that enhances cationic Upid-mediated gene transfer. Bioconjug Chem 12 906-910. 

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