Mediator ion

Lonart G, Johnson KM Inhibitory effects of nitric oxide on the uptake of [3H]dopamine and [3H]glutamate by striatal synaptosomes. J Neurochem 63 2108—2117, 1994 Lovinger DM, White G Ethanol potentiation of 5-hydroxytryptamine3 receptor-mediated ion current in neuroblastoma cells and isolated adult mammalian neurons. Mol Pharmacol 40 263—270, 1991... 

Apart from the study of physicochemical aspects such as ion solvation, and bio-mimetic aspects such as photosynthesis or carrier-mediated ion transfer (Volkov et al., 1996, 1998), there are several areas of potential applications of electrochemical IBTILE measurements comprising electroanalysis, lipophilicity assessment of drugs, phase transfer catalysis, electro-assisted extraction, and electrocatalysis. 

The study of McMillan-Mayer level models, in which the solvent coordinates have been averaged over so that only solvent-mediated ion-ion forces need be treated, is relatively well developed. However the real forces at this level are even more poorly known than the forces at the Born-Oppenheim level referred to above. It is found that McMillan-Mayer level models can be brought into good agreement with solution thermodynamic data. 

R.E. Asenstorfer, Y. Hayasaka and G.P. Jones, Isolation and structures of oligomeric wine pigments by bisulfite-mediated ion-exchange chromatography../. Agric. Food Chem. 49 (2001) 5957-5963. 

A superficial examination of experimental results obtained by using labeling techniques (electrodialytic transport through solvent polymeric membranes) indicates that there might be a substantial transport of water coupled with the carrier-mediated ion transport. This would be rather surprising because the cation in the carrier-cation complex is not hydrated. 

Ionophore-mediated ion transport (down electrochemical gradient)... 

It is well known that TEA is able to inhibit K+-channel mediated ion transport at both sides of plasma membranes [53, 54], and the present observations are consistent with this unique characteristic. 

Thus, the extractant-mediated ion-exchange process (Equation 11.9) can result in substantial indirect solubilization losses of the IL cation. In fact, at sufficiently... 

Alkali metal transport in biochemistry is a vital process in maintenance of cell membrane potentials of use, for example, in nerve signal transduction and is at the core of some of the early work on artificial ionophores that mimic natural ion carriers such as valinomycin. Ionophore mediated ion transport is much slower than transport through cation and anion ion channel proteins, however. 

The preparation can also take place under acidic conditions below the isoelectric point of the Si-OH-bearing inorganic species (pH 2) then the silica species are positively charged, that is, protonated silanol groups (Si-OHT) in order to produce an interaction with cationic surfactants, it is necessary to add a mediator ion X- (usually a halide), which gives rise to the S+X I+ pathway (Fig. 3.6b). 

Conversely, when negatively charged surfactants (e.g., long-chain alkyl phosphates) are used as SDAs, it is possible to work in basic media, whereby again a mediator ion, in this case a positively charged one (M+), must be added to... 

When working in acidic media and using negatively charged surfactants a mediator ion is not required the S I+ pathway (Fig. 3.6d). 

The mechanisms are easily distinguished. The homogeneous mechanisms lead to rates that are proportional to the concentrations of the mediator ions in solution and continue after the current is switched off (until the high valency form ofthe ions is consumed). The direct oxidation process stops when the current is turned off. 

The actual mechanism of channel-mediated ion transport is, so far, not established unequivocally. Alternative possibilities exist, sucb as formation of tubular bundles with holes large enough to serve as a conduit for water and ions. 

Much effort has been expended in attempting to use membranes for separations. Reverse osmosis membranes are used worldwide for water purification. These membranes are based on size selectivity depending on the pores used. They do not have the ability to selectively separate target species other than by size. Incorporation of carrier molecules into liquid membrane systems of various types has resulted in achievement of highly selective separations on a laboratory scale. Reviews of the extensive literature on the use of liquid membrane systems for carrier-mediated ion separations have been published [15-20]. A variety of liquid membranes has been studied including bulk (BLM), emulsion (ELM), thin sheet supported (TSSLM), hollow fiber supported (HFSLM), and two module hollow fiber supported (TMHFSLM) types. Of these liquid membranes, only the ELM and TMHFSLM types are likely to be commercialized. Inadequacies of the remaining... 

The pore formation mechanism presented in Fig. 7 (45) is appealing for many reasons. It illustrates the significance of thermal fluctuations, because the pore is indeed induced by fluctuations in spontaneous salt ion concentrations in the vicinity of the membrane. Furthermore, the pore mediated ion leakage mechanism is very rapid, and it occurs in a collective manner through redistribution and diffusion of lipids around the pore. Also, recent data indicate that the pores also mediate flip-flop events across a membrane (46), which provides one plausible mechanism for lipid translocation, which in turn is of central importance in processes such as programmed cell death. Other dynamic processes in lipid systems are expected to be equally complex, which highlights the importance to understand the interplay between thermal fluctuations, physiologic conditions, and collective phenomena. 

One of the most important categories of ion selective chemical sensors is based on what are called liquid membranes. This term was flrst used in 196U to describe a matrix that is not water soluble it contains either anionic or cationic sites (liquid ion exchangers), which can selectivity facilitate the exchange of inorganic ions. In order to study the active carrier-mediated ion transport through these liquid membranes, a cell such as the one shown in Figure 3.4.4 has been employed. 

Preparation of the primary oligomeric clusters has been discussed in terms of the association of the ions in electrolyte solutions or condensation-mediated ion clustering. Dependent on the electrolyte concentration and the physicochemical state (P, T, pS, pH, pi, pCl, pc, pe) of the system, the ions associate to polymeric species or then the ion clusters may reach the critical size that enables them to grow to primary particles of some 100 mn in size. As discussed, they are probably a coagulate of cemented crystallites of 1 to 10 mn size. However, to be useful for further processing, these must be stabilized to sols, i.e., to a stable dispersion of particles of colloidal (10 to 1000 mn) size. There are basically two approaches for the stabilization ... 

Carrier Mediated Ion Transport through Artificial and Biological... 

Fig. 18. Mechanism of carrier-mediated ion transport through a lipid bilayer membrane [Reproduced from Stark, G., et.al Biophys. j. 11, 981 (1971) and Benz, R., Stark, G. Biochem. Biophys. Acta 382 (1), 27 (1975).]...

Despite its complex formation ability, antamanide does not mediate ion transport through artificial or biological membranes. This is probably due to its poor... 

Kaplan, J. Hi, Passow, H. Hoppe Seyler s Z. Physiol Chem. 355 (10), 1215 (1974). Proceedings Asymmetric effects of phlorizin on valinomycin-mediated ion movements across the human erythrocyte membrane... 

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