Metals, heavy chelators

This dye fluoresces after binding Pb+2 and Ca+2 lead is considered an interferant to the determination of calcium by this approach. However, by complexing the divalent lead ion with the heavy metal chelator TPEN (N,N,N ,N -tetrakis(2-pyridylmethyl)ethylene-diamine) prior to the addition of the fluo-3, the fluorescent... 

Koehler, F.M., Rossier, M., Waelle, M., Athanassiou, E.K., Limbach, L.K., Grass, R.N., Gunther, D. and Stark, W.J. (2009) Magnetic EDTA coupling heavy metal chelators to metal nanomagnets for rapid removal of cadmium, lead and copper from contaminated water. Chemical Communications, (32), 4862—4864. 

Pharmacology Succimer is an orally active, heavy metal chelating agent it forms water soluble chelates and, consequently, increases the urinary excretion of lead. Pharmacokinetics In a study in healthy adult volunteers, after a single dose of 16, 32, or 48 mg/kg, absorption was rapid but variable, with peak blood levels between 1 and 2 hours. Approximately 49% of the dose was excreted 39% in the feces, 9% in the urine, and 1 % as carbon dioxide from the lungs. Because fecal excretion probably represented nonabsorbed drug, most of the absorbed drug was excreted by the kidneys. The apparent elimination half-life was about 2 days. 

Raspor, B., Valenta, P., Nurnberg, H.W. and Branica, M., 1978. The chelation of cadmium with NTA in seawater as a model for the typical behaviour of trace heavy metal chelates in natural waters. Sci. Total Environm., 9 87-109. 

We will not go in depth into the subject of antioxidants (12), which is more a part of preformulation than a stress test, but the autoxidation mechanism does suggest that oxidation can be inhibited by peroxy radical scavengers (chain-breaking antioxidants) like phenol antioxidants, by heavy metal chelating agents, and by peroxide inactivating substances (preventive antioxidants). 

They acknowledge that the exact mechanism of the adsorption of heavy metal chelates is quite complex but do not hesitate to propo.se the formation of an electron donor-acceptor complex of the chelate and the active sites (e.g., carbonyl groups) and possible beneficial effect of hydrogen bonding between the... 

Boyce N, Wood C, Holdsworth S, Thomson NM, Atkins RC. Life-threatening sepsis compUcating heavy metal chelation therapy with desferrioxamine. Aust NZ J Med 1985 15(5) 654-5. 

Stevens PE, Moore DF, House IM, Volans GN, Rainford DJ. Significant ehmination of bismuth by haemodialysis with a new heavy-metal chelating agent. Nephrol Dial Transplant l995 l0(5) 696-8. 

Hossain MA., Piyatida P., da Silva JAT., Fujita M. Molecular mechanism of heavy metal toxicity and tolerance in plants central role of glutathione in detoxification of reactive oxygen species and methylglyoxal and in heavy metal chelation. Journal of Botany 2012 Article ID 872875, 37 pages. 

The heavy-metal chelating properties of thiols were taken advantage of in the design of dimercaprol ( British Anti-Lewisite, BAL) as counter poison of the arsenical war gas lewisite (Figure 20.43). Today dimercaprol is used to treat poisoning by compounds of gold, mercury, antimony and arsenic. The toxic nature of the heavy metals is masked and chelate is stable enough to be excreted as such in the urine. 

Adler, M., Dinterman, R.E., and Wannemacher, R.W. 1997. Protection by the heavy metal chelator N,N,N, A -tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) against the lethal action of boUilinum neurotoxin A and B. Toxicon 35 1089-1100. 

Adler, M., Shafer, H., Hamilton, T., and Petrali, J.P. 1999b. Cytotoxic actions of the heavy metal chelator TPEN on NG108-15 neuroblastoma-glioma cells. Neurotoxicology 20 571-582. 

Sheridan, R.E. 1996. Protonophore antagonism of botulinum toxin in mouse muscle. Toxicon 34 849-855. Sheridan, R.E. and Deshpande, S.S. 1995. Interaction between heavy metal chelators and botuhnum neurotoxin... 

Other potential blister agents include lewisite and phosgene oxime (CG). Lewisite was synthesized during the late stage of WWl, but there are no reports of its battlefield use. Its antidote, British Anti-lewisite, finds medicinal use today as a heavy metal chelator. Although classified as a vesicant, CG is a corrosive urticant for which, like lewisite, there are no reports of battlefield use. There are also no reports of CNS effects following intoxication with these agents. 

Metal species bound with organics (heavy metals chelates, organometallic... 

Succimer, a heavy-metal-chelating agent, is used in the treatment of lead poisoning in children with blood levels about 45 mcg/dl. Succimer forms water soluble chelate with lead, increasing the urinary excretion. 

Trientine, a heavy-metal-chelating agent (750 to 1250 mg in divided doses), is used in Wilson s disease in patients who are intolerant of penicillamine. 

Protein denaturation can be due to physical reasons, e.g. heat (Figure 8.42), cold, mechanical forces, radiation or influence of chemical factors (acids, alkali, salts, solvents, surfactants, oxidants, heavy metals, chelating agents). 

Kunkel, R. and Manahan, S.E., 1973. Atomic absorption analysis of strong heavy metal chelating agents in water and waste water. Anal. Chem., 45 1465—1468. 

Higgins et al. (1999) developed a system for the detection of Staphylococcus enterotoxinB (SEB), ricin toxin. Yersinia pestisYl antigen and 5ac/7/MX anthracis PA antigen based on the principle of electrochemiluminescence (ECL). ECL is a process that involves the generation of light from a voltage-dependent, cyclic oxidation-reduction reaction of rathenium heavy metal chelate. The redox... 

A further application of TLRC in the biochemical field is in the assessment of the activity of enzymes, where TLRC can be used to monitor and quantitate the products during the course of an enzyme reaction such as deiodination. Other examples of the use of TLRC in biochemical studies are the qualitative assessment of the complex-forming ability of metals and ligands in biological systems and the complex formation of heavy metal chelates, such as molybdenum species with poly-aminocarboxylic acids. 

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