Stoichiometric displacement

Drager, R. R. and Regnier, F. E., Application of the stoichiometric displacement model of retention to anion-exchange chromatography of nucleic acids,... 

Roush, D. J., Gill, D. S., and Willson, R. C., Anion-exchange chromatographic behavior of recombinant rat cytochrome b5. Thermodynamic driving forces and temperature dependence of the stoichiometric displacement parameter Z, /. Chromatogr., 653, 207, 1993. 

A stoichiometric model can conveniently be invoked to explain the ion-exchange retention process [43 6]. As discussed in detail in these cited papers on ion-exchange theory, useful information about the involved ion-exchange process can be deduced from plots of log k vs. the log of the counterion concentration [X], which commonly show linear dependencies according to the stoichiometric displacement model (Equation 1.1)... 

A thorough study on the ion-exchange mechanism and the effect of distinct counterions in this PO mode was recently presented by Gyimesi-Forras et al. [41]. A large variety of distinct acid additives to methanol, acetonitrile, and tetrahydrofuran (Table 1.1) (without any base added) was investigated in view of the stoichiometric displacement model and their effect on the enantiomer separation of 2-methoxy-2-(l-naphthyl)propionic acid. The stoichiometric displacement model (Equation 1.1) was obeyed also in the PO mode, as revealed by linear plots of log k vs. acid concentration. The slopes and intercepts along with the concentration ranges used with the distinct competitor acids are summarized in Table 1.1. 

Influence of Acid Additives on Retention Characteristics of 2-Methoxy-2-(1-Naphthyl)Propionic Acid on a 0-9-(tert-ButylcarbamoyOQuinine CSP as Assessed by the Characteristic Parameters of the Stoichiometric Displacement Model (Slopes and Interc ... 

According to the stoichiometric displacement model, the equilibrium constant for peptide adsorption with the solvated nonpolar ligands can be expressed as follows ... 

A novel method for synthesizing polythiaether macrocycles with Re cluster complex was proposed by Adams and coworkers [185]. This process involves catalysis by the Re complex rather than the stoichiometric displacement of dithiol or dithiolates by organic halides, and first example of a catalytic procedure for synthesis of polythiaether macrocycle using thietanes. The macro-cyclic products formed are shown in Fig. 56. 

Although the stoichiometric displacement model does not describe the physical situation rigorously enough, it has been widely used and corrected for some shortcomings. Whitley et al.m 89 have corrected the model since not all charges are accessible for the protein. They have introduced a correction... 

The basic principles of ion exchange have been discussed by Walton [78]. However, this discussion was mainly limited to the case of small inorganic ions. For the separation of biomolecules, e stoichiometric displacement model (SDM, next subsection) is of particular interest. This model is based on the assumption that ion exchange is the only mechanism of retention of the components studied and that the ion-exchange process can be modeled as a stoichiometric "reaction" described by the mass action principle. 

The state of equilibrium in ion exchange chromatography is currently described by stoichiometric models where the solute, for example a protein, displaces a stoichiometric number of salt ions bound on the ion exchanger. A basic concept is the stoichiometric displacement model developed by Kopaciewicz et al. (1983). For monovalent counterions the reaction is described as follows ... 

The importance of three-dimensional structure to chromatographic behavior is reflected in the nonmechanistic model, the stoichiometric displacement model (SDM). The central hypothesis of the SDM is that the displacement of a solute from a surface is accompanied by the adsorption of a stoichiometric amount of displacing agent. The process may be described by the equilibrium expression ... 

Adsorption from solution may be represented by a stoichiometric displacement reaction between molecules of the adsorbed solvent (water, component 2) and the solute (surfactant, component 1) [10-12] ... 

X. Geng and F. E. Regnier, J. Chromatogr., 332,147 (1985). Stoichiometric Displacement of Solvent by Non-Polar Solutes in Reversed-Phase Liquid Chromatography. 

Various sympathomimetic amines can be taken up into storage vesicles, leading to the stoichiometric displacement of part of the endogenous NA content (p-tyramine and -phenylethylamine). It is not clear that such amines are taken up by the same mechanism which is responsible for catecholamine uptake. For example, metaraminol is taken up by medullary vesicles by a process which does not require ATP. and is insensitive to inhibition by reserpine. Some amines, such as DA and -methylNA. appear to be taken up both by the reserpine-sensitive and reserpine-insensitive mechanisms. It may be that the latter mechanism can account for the uptake of exogenous catecholamines into storage vesicles in reserpine-treated animals, leading to a temporary restoration of adrenergic transmission. 

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