Manganese EDTA chelate

Mixtures of manganese, magnesium, and zinc can be similarly analysed. The first EDTA end point gives the sum of the three ions. Fluoride ion is added and the EDTA liberated from the magnesium-EDTA complex is titrated with manganese ion as detailed above. Following the second end point cyanide ion is added to displace zinc from its EDTA chelate and to form the stable cyanozincate complex [Zn(CN)4]2- the liberated EDTA (equivalent to the zinc) is titrated with standard manganese-ion solution. 

The rate of peroxide decomposition and the resultant rate of oxidation are markedly increased by the presence of ions of metals such as iron, copper, manganese, and cobalt [13]. This catalytic decomposition is based on a redox mechanism, as in Figure 15.2. Consequently, it is important to control and limit the amounts of metal impurities in raw rubber. The influence of antioxidants against these rubber poisons depends at least partially on a complex formation (chelation) of the damaging ion. In favor of this theory is the fact that simple chelating agents that have no aging-protective activity, like ethylene diamine tetracetic acid (EDTA), act as copper protectors. 

The heavy metals copper, manganese, cobalt and zinc were omitted individually and in combination from MS and B5 media to determine the effect on antibody stability in solution [63]. When IgG, antibody was added to these modified media in experiments similar to the one represented in Figure 2.2, only the B5 medium without Mn showed a significant improvement in antibody retention relative to normal culture media. Nevertheless, protein losses were considerable as only about 30% of the added antibody could be detected in the Mn-free medium after about 5 h. The beneficial effect of removing Mn was lost when all four heavy metals, Cu, Mn, Co and Zn, were omitted simultaneously. The reason for these results is unclear. Addition of the metal chelating agent ethylenediaminetetraacetate (EDTA) had a negligible effect on antibody retention in both MS and B5 media [63]. 

Edetate calcium disodium is indicated chiefly for the chelation of lead, but it may also have usefulness in poisoning by zinc, manganese, and certain heavy radionuclides. In spite of repeated claims in the alternative medicine literature, EDTA has no demonstrated usefulness in the treatment of atherosclerotic cardiovascular disease. 

It may also be necessary during treatment to supplement the diet with those trace metals which are also chelated by EDTA. Computer simulation models of the selectivity for lead(ii) ions revealed, later to be verified by urine monitoring, that some manganese and zinc ions are co-excreted. Once having been established it is easy to rectify such phenomena by orally topping up with the appropriate salts. 

Another advantage of potentiometric titrations is that substances to which the electrode does not respond can be determined, if the electrode responds to the titrant or to some low level of an indicator substance that has been added to the solution. For example, low levels of Al can be determined by titration with standard fluoride solution, using a fluoride electrode [22]. EDTA and other chelates can be determined by titration with standard calcium or copper solution. Manganese(II), vanadium(II), or cobalt(II) can be determined via EDTA titration if a small amount of CuEDTA indicator is added to the solution and a copper electrode is used. The electrode responds directly to the Cu activity which, however, is dependent on the activities of the EDTA and the other metal ion in solution. 

The therapeutical use of CujZujSuperoxide dismutase as scavenger for the potentially toxic superoxide anion is limited on very special events The half-time of circulation in the organism is very short and it is unable to pass cellular membranes. As a consequence it was attempted to search for lipophilic substances, able to catalyze the dismutation of superoxide, but resistant to biological chelators. One approach was the use of different metalloporphyrins. Some iron and manganese prophyrins catalyze the disnxutation of superoxide with about 3 % efficiency of native CUjZnj-SOD 268) Apart from copper porphyrins, which are inactive as superoxide dismutases, no copper complexes have been described which are at the same time scavengers of superoxide and stable to proteins or EDTA. 

A similar terpyridine based chelate is marketed (Perkin-Elmer) as Eu-W8044 DTA chelate 4 and has a dichlorotriazinyl group as a reactive arm [39]. Again the nonadentate complexation increases the stability, the fluorescence is stable at pH 5 and decreases by 20% within 2 h incubation in 50 mM succinate pH 4, but 90% of the fluorescence is lost at pH 3 (the difference of behavior with the Eu-TMT vide supra could be due to the difference in buffer composition). The Eu-W8044 is also more stable in the presence of EOT A and can withstand 2 h in 250 mM EDTA pH 7.8, but manganese effect is still detrimental since 80% of the fluorescence is lost within 30 min in the presence of 100 pM Mn " as described above for the heptadentate Eu-W 1024 chelate, a calculated amount of EDTA cancels the manganese effect (www.perkinelmer.com/lifesciences, Stability of the Wallac LANCE Eu-chelates ). 

Finally, control by a chelating agent, EDTA, seems logical. A derivation indicated that the predicted rate ratios would be 10. The predicted rate ratio was improved using formation constants for protonated species for iron, but not manganese, and the chelation approach was not pursued further (19). 

Metal Chelators. Naturally occurring and synthetic substances which can chelate manganese or magnesium tend to be very strong inhibitors of PEP carboxylase. At Km levels of magnesium, 1 mM EDTA will inhibit nearly 100%, as will citrate. Nucleotides such as ATP and ADP, but not AMP will also inhibit at 1 mM concentrations (Table 4.4). One can readily visualize therefore a possible regulatory function for ATP and ADP in tissues with PEP carboxylase-mediated reactions. 

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