Competitive complex formation

J. Wang, B.S. Grabaric, Application of adsorptive stripping voltammetry for indirect measurement of nonelectroactive ions using competitive complex formation reactions, Mikrochim. Acta 100 (1990) 31-40. 

The reaction control should be emphasized amongst the conditions of reactions of competitive complex formation [19,23], It is necessary to take into account that it is possible to determine, and frequently predict, the direction of the electrophilic attack to the donor center of di- and polyfunctional donors (ligands) only in the case when the thermodynamically stable products are formed under conditions of kinetic control. Thus, the thermodynamic stability of complexes is discussed, when the bond between the metal and di- and polydentate ligands is localized in the place of primary attack on one of any of the donor centers by the electrophilic reagent, without further change of coordination mode in the reaction of complex formation. 

Deprotonated surface hydroxyls exhibit Lewis base behavior. Adsorption of metal ions is therefore understood as competitive complex formation involving one or two surface hydroxyl groups ... 

If we assume that no ternary complexes [HAG] are formed, can be determined from competitive complex formation ... 

The reactivity of biotin with several reagents can be exploited in some chemical assays like its reaction with diazo derivatives, or the reaction of the ureido ring with p-dimethylaminocinnamaldehyde in an acidic medium, but the sensitivity of these assays is relatively poor. Several methods described for biotin assay involve a competitive complex formation between biotin and avidin bound with a chromophore/ fluorophore probe. In these assays, biotin, which has a higher affinity for avidin, quantitatively displaces the probe from the complex. 

Digiuni, S., Schellmann, S., Geier, F., Greese, B., Pesch, M, Wester, K, Dartan, B., Mach, V., Srinivas, B.P., Timmer, J., Fleck, C. Hiilskamp M. (2008). A competitive complex formation mechanism underlies trichome patterning in Arabidopsis leaves. Molecular Systems Biology, Vol.4, Article 217. 

Addition of four equivalents of boric acid to the starting ketose improves the original 6.5% yield of D-hamamelose up to 20% [55]. Thus, the product of the molybdic acid catalyzed rearrangement, D-hamamelose, is apparently being removed from its thermodynamic equilibrium with D-fructose by a competitive complex formation with boric acid. 

Krug A, Kellner R (1994) Determination of eitrie aeid by means of competitive complex formation in a flow injection system. Mikroehim Aeta 113 203-210 Ni Y (1998) Simultaneous detemninalion of mixtures of acids by potentiometric titration. Anal Chim Acta 367 145-152... 

Most modem RJAs utilize a competitive assay format (Fig. 2) in which radiolabled antigen, Ag, competes with unlabeled antigen, Ag, in a sample for binding to the antibody. Ah. The free antigens are then separated from the antigen—antibody complexes, and the amount of radioactivity in the... 

Most immunoassay kits and many commercial immunoassay analyzers are based on heterogenous EIA or FIA. These include an immunoassay system that uses FIA linked to radial partition chromatography of the antibody—antigen complex (39) a system that uses antibody-coated tubes for enzyme immunoassay of a variety of hormones and dmgs (40) and a system that uses either a sandwich or competitive FIA format to measure a variety of analytes (41). 

An inhibitor that binds exclusively to the free enzyme (i.e., for which a = °°) is said to be competitive because the binding of the inhibitor and the substrate to the enzyme are mutually exclusive hence these inhibitors compete with the substrate for the pool of free enzyme molecules. Referring back to the relationships between the steady state kinetic constants and the steps in catalysis (Figure 2.8), one would expect inhibitors that conform to this mechanism to affect the apparent value of KM (which relates to formation of the enzyme-substrate complex) and VmJKM, but not the value of Vmax (which relates to the chemical steps subsequent to ES complex formation). The presence of a competitive inhibitor thus influences the steady state velocity equation as described by Equation (3.1) ... 

For the biological limitation of trace metal internalisation, complex formation will invariably decrease the concentration of free metal ion and thus decrease the biouptake fluxes and carrier-bound metal (FIAM, BLM). In the case of a diffusion-limited internalisation, complex labilities and mobilities become much more pertinent when determining uptake fluxes. As shown earlier, few experiments have been designed to identify diffusion limitation of metal uptake fluxes, despite the fact that such a limitation is possible (Figure 10). Competition experiments that can distinguish a kinetic from a thermodynamic control are rare. In these areas, an important research focus is... 

As evidenced by the mass laws of Eqs. (2.8), (2.9), the binding of a metal ion by. surfaceJigands - similar to the binding of a metal ion by a solute ligand - js strongly pH dependent (Fig. 2.5a). Complex formation is competitive (e.g., metal ion vs H+ ion or vs.another metal ion). Fig. 2.5b illustrates the sorption of various metal ions on hydrous ferric oxide. For each metal ion there is a narrow interval of 1 - 2 pH un.ita where the extent of sorption rises from zero to almost 100 %. 

The main mechanism of ligand adsorption is ligand exchange the surface hydroxyl is exchanged by another ligand. This surface complex formation is also competitive OH ions and other ligands compete for the Lewis acid of the central ion of the hydrous oxide (e.g., the Al(iii) or the Fe(III) in aluminum or ferric (hydr)oxides). The extent of surface complex formation (adsorption) is, as with metal ions, strongly... 

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