Lead ion toxicity

Even the application of Ti/Pb02 anodes to wastewater treatment may be limited by the possible release of toxic lead ions, due to their dissolution under specific anodic polarization and solution composition. 

Steps have been taken by the World Health Organization (WHO) and the U.S. Environmental Protection Agency (EPA) to reduce the amount of toxic metal ions in the environment. For example, large concentrations of lead have been shown to be lethal to humans. The maximum amount of lead tolerated in drinking water according to the WHO and the EPA, is 0.05 mg/l(9l) and 0.5 mg/I,(92) respectively. For this reason, innovative techniques to measure low concentrations of metal ions are emerging. 

Several papers have been devoted to the detection of toxic metal ions. Some of the probes developed for toxic metals include a selective neutral ionophore for lead... 

Ferrochelatase (protoheme ferro-lyase)401 403 inserts Fe2+ into protoporphyrin IX to form heme. The enzyme is found firmly bound to the inner membrane of mitochondria of animal cells, chloroplasts of plants, and chromatophores of bacteria. While Fe2+ is apparently the only metallic ion ordinarily inserted into a porphyrin, the Zn2+ protoporphyrin chelate accumulates in substantial amounts in yeast, and Cu2+-heme complexes are known (p. 843). Ferrochelatase, whose activity is stimulated by Ca2+, appears to be inhibited by lead ions, a fact that may account for some of the acute toxicity of lead.404... 

Early life forms thriving near thermal vents in waters enriched in heavy metal ions would have had to have been endowed with mechanisms to deal with toxic metal ions and it is conceivable that efflux mechanisms for these metals evolved before or concomitandy with their use as cofactors. In line with such a hypothesis, the CPx-type ATPases encompass a wider spectrum of ion specificities than the non-heavy metal ATPases, now including Cu+, Ag+, Zn +, Cd +, and Pb. It is to be expected that other metal ions will be added to this list. ATPases transporting silver, zinc, cadmium, and lead are involved in bacterial resistance to these toxic metal ions, while copper-transporting ATPases have a role both in copper uptake to meet cellular demands and in copper extrusion when ambient... 

SM forms sulfonium ion in the body and alkylates DNA leading to DNA strand breaks and cell death. Due to the high electrophilic property of the sulfonium ion, SM binds to a variety of cellular macromolecules (Somani and Babu, 1989 Dacre and Goldman, 1996). The most common complications of SM occur in lung, skin, and eye which are the principal target organs due to its direct effect. The systemic toxicity leads to several manifestations (Balali-Mood et al, 2005 Dacre and Goldman, 1996). 

Thielemann, H. Thin-layer chromatographic detection limits (semiquantitative determination) of toxic metal ions (lead, mercury, zinc, copper). Z. Chem. 15, 110 (1975) see also Z. Anal. Chem. 275, 206 (1975)... 

Srivastava S.K., R, Tyagi, N. Pant, and N. Pal. 1989. Studies on the removal of some toxic metal ions. Part II. Removal of lead and cadmium by montmorillonite and kaolinite. Environ. Technol, Lett. 10 275-282. 

The plasma membrane of cells is one of the main targets for toxic metals, such as lead and zinc. However, the ceU mechanisms of toxic action of these metals are not completely clear. Therefore, a study of the fine structure of erythrocyte membranes under the action of toxic and potentially toxic metal ions is of major... 

The activity of an enzyme is destroyed if some molecule other than the substrate specific to that enzyme binds to the active site and blocks entry of the substrate. Such substances are called enzyme inhibitors. Nerve poisons and certain toxic metal ions, such as lead and mercury, are believed to act in this way to inhibit enzyme activity. Some other poisons act by attaching elsewhere on the enzyme, thereby distorting the active site so that the substrate no longer fits. 

Lead chromate has been used as a pigment, although both the lead ion and the chromate ion are toxic. What is the molar solubility of PbCr04 in water ... 

Phytochelatin a plant peptide produced in response to lieavy metals, e.g. cadmium, copper, mercury, lead and zinc. The structure is (Y-Glu-Cys) -Gly (n = 3-7). Like Metallothionein (see), P. form metal-thiolate bonds and thus sequester toxic metal ions. They are probably derived from glutathione rather than RNA-directed protein synthesis. 

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