Protein chelated metals

Aime, S. Fasano, M. Terreno, E. Botta, M. Protein-bound Metal Chelates. In The Chemistry of Contrast Agents in Medical Magnetic Resonance Imaging Toth, E., Merbach, A. E., Eds. Wiley, Chichester, UK, 2001 pp 193-241. 

Note that it is important to avoid carboxy cation exchangers. A proportion of the charged groups on a carboxy cation exchanger exist in a relative proximity that endows them with the ability to chelate metal ions. These chelating sites may competitively displace metals from proteins in the sample, creating a source of assay variability. Use a noncarboxy cation exchanger such as sulfomethyl, ethyl, or propyl. 

In order to understand the interactions of proteins with metals, it is necessary to consider the effect of pH on the stability of metal chelates.78,78 The following, simplified treatment illustrates the equilibria that can occur between a metal ion, a chelating agent (or other ligand), and hydrogen ion. Although it is almost impossible to apply the equations quantitatively to metalloenzymes, they do illustrate the interactions of the different variables. 

Once the fungicides penetrate to the cell membrane or into the cytoplasm they may operate by devious means to disrupt vital functions. There is substantial evidence that the quinones immobilize the sultliydryl and imino prosthetic group of enzymes. The 8-hydroxyquinoline and dithiocarbamate compounds are active against copper and other metallic members of an enzyme system, presumably hy their ability to chelate metals. Heavy metals such as mercury alTect certain enzymes such as amylases and may serve as general protein precipitants. 

El Rassi and Horvath185 could fit the logarithmic retention factor of proteins on metal-chelate sorbents by a three-parameter equation ... 

In practice alkaline pH favors the selectivity of adsorption of antibodies on chelated metal ions on solid phases. To achieve high levels of antibody purity a wash with 0.5-1 M sodium chloride can be helpful to desorb weakly interacting proteins.190... 

Li-Chan, E., Kwan, L., and Nakai, S. (1990). Isolation of immunoglobulins by competitive displacement of cheese whey proteins during metal chelate interaction chromatography. J. Diary Sci. 73, 2075-2086. 

Although most of the compounds produced hy Alternaria are generally nontoxic, altemariol monomethyl ether has been shown to be mutagenic in bacteria (Ames tests) [166]. Tenuazonic acid (TA) is a protein synthesis inhibitor and is capable of chelating metal ions and forming nitrosamines. TA is also produced... 

Soon afterward, Kronman, who has made a long study of a-lactalbumin reactions, considered that there was an experimental artifact in the use of chelating metal ion buffers (e.g., EGTA and EDTA) in the determination of association constants for metal ions with proteins by fluorescence titration. Kronman and Bratcher (1983) concluded that their observations explained the discrepancy between As,i for Ca(ll) and bovine a-lactalbumin reported by Kronman et al. (1981) (2.7 X 10 M ), Permyakov et al. (1981) (6.3 X 10 M" ), and Murakami et al. (1982) (4 x 10 Af- ). 

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