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Toxicity from transition metal ions

The third environment of interest to farmers and horticulturists is the land itself. The primary criterion here is that particulate materials, whether of biological origin or not, should be small enough not to interfere with root growth. Undue amounts of woody materials can reduce compost quality, as can large pieces of plastic film (> 50 x 50 mm) that may interfere with root penetration. Other criteria of quality are toxicity to macroorganisms in the soil (worms, daphnia, etc) and possible toxicity to plants and the animals that eat them from transition metal ions (see Section 9). [Pg.454]

Injury to cells and tissues may enhance the toxicity of the active oxygen species by releasing intracellular transition metal ions (such as iron) into the surrounding tissue from storage sites, decompartmentalized haem proteins, or metalloproteins by interaction with delocalized proteases or oxidants. Such delocalized iron and haem proteins have the capacity to decompose peroxide to peroxyl and alkoxyl radicals, exacerbating the initial lesion. [Pg.45]

Metal Complexation. Azo dyes containing hydroxy or carboxylic acid gronp substituents adjacent to the azo gronp react with transition metal ions, e.g. chromium, cobalt and copper to produce complexes, e.g. Cl Acid Violet 78 (2.15)7 These metal complex dyes are more stable to light than their unmetallised precursors and have been widely nsed as dyes for polyamide and wool fibres. However, there is now a move away from chrominm complexes due to toxicity concerns (see section 2.3.2.). [Pg.90]

Researchers at Oregon State University are currently studying apphcations of chitosan beads for the removal of toxic metal ions from wastewater. Chitosan has potential applications to waste removal because it selectively adsorbs toxic Group III transition metal ions in preference to less dangerous alkali or alkaline earth metal ions. The technology has been the focus of bench-scale studies and is not commercially available but it is available for licensing. [Pg.845]

However, the superoxide dismutase may be overwhelmed by the amount of superoxide being produced after a toxic dose of paraquat. The superoxide may then cause lipid peroxidation via the production of hydroxyl radicals. These may be produced from hydrogen peroxide in the presence of transition metal ions (see chap. 6). [Pg.338]

In biological studies, apart from alkali and alkaline earth cations, zinc sensing is very important, especially in neuroscience. Binding of zinc and other (often toxic) transition metal ions requires receptors of different structure and coordination properties. Polypyridines, dendritic pyridines, and thiacrown ethers are the receptors of choice. [Pg.264]

Unlike Cr(VI), a recognized human carcinogen (Section III. A) (2), Cr(III) is often considered as one of the least toxic transition metal ions on the basis of its poor absorptivity and kinetic inertness, as well as from the lack of acute toxicity of large doses of Cr(III) compounds in rats (3). A concern about the safety of the use of Cr(III) in food supplements firstly arose after the finding of Stearns et al. (607) that Xlla (0.050-1.0 mM Cr) caused chromosome damage in culmred mammalian cells. In addition, mutations in the hprt locus, ultrastmcmral... [Pg.217]

The accumulation of toxic transition metal ions from the plastics in the stems, leaves, fruit and tubers from the growing of soft fruits and vegetables. Table 8 [24] shows that even if the soil is loaded with much higher concentrations of Ni salts than can ever be obtained from degraded plastic films, the plants take up only the amount of... [Pg.473]

The commonly used transition metal compounds in commercial oxo-biodegradable plastics are manganese, iron, cobalt and nickel. None of these have been shown to be toxic and until recently have not been in national lists of dangerous substances. All the above transition metal ions, which are required in human nutrition, are absorbed from foodstuffs and water. They are therefore considered to be essential minerals [70] required in oxygen transport systems. The non-toxicities of iron, which is present in haemoglobin, catalase and peroxidases and of manganese, required for manganese peroxidase, have not been questioned. [Pg.246]

The future challenge is to develop cathodes with simple transition-metal layered oxides in which at least one lithium ion per transition-metal ion could be reversibly extracted/inserted while keeping the materials cost and toxicity low such a cathode can nearly double the energy density compared to the present level. There are also possibilities to increase the capacity of cathode hosts perhaps by focusing oti nanosized powders and amorphous materials. From a safety, cycle and shelf life points of view, such cathodes with a voltage lower than 4.5 V, but with a significantly increased capacity are desirable for future applications. [Pg.151]

The vast majority of biochemical processes in which a metal plays a role involve a only a relatively small number of metals. Those metals include Na, K, Mg, Ca, Mo, or the first-row transition metals from V to Zn. Only molybdenum could be considered as a heavy metal. It should also be observed that the metal ions constitute those that can be considered as hard or borderline in hardness. It is a general property that ions of heavy metals having low charge (that is to say "soft") are toxic. These include Hg, Pb, Cd, H, and numerous others. Some heavy metals bind to groups such as the sulfhydryl (-SH) group in enzymes, thereby destroying the ability of the enzyme to promote the reaction in a... [Pg.802]

Many transition metal complexes have been considered as synzymes for superoxide anion dismutation and activity as SOD mimics. The stability and toxicity of any metal complex intended for pharmaceutical application is of paramount concern, and the complex must also be determined to be truly catalytic for superoxide ion dismutation. Because the catalytic activity of SOD1, for instance, is essentially diffusion-controlled with rates of 2 x 1 () M 1 s 1, fast analytic techniques must be used to directly measure the decay of superoxide anion in testing complexes as SOD mimics. One needs to distinguish between the uncatalyzed stoichiometric decay of the superoxide anion (second-order kinetic behavior) and true catalytic SOD dismutation (first-order behavior with [O ] [synzyme] and many turnovers of SOD mimic catalytic behavior). Indirect detection methods such as those in which a steady-state concentration of superoxide anion is generated from a xanthine/xanthine oxidase system will not measure catalytic synzyme behavior but instead will evaluate the potential SOD mimic as a stoichiometric superoxide scavenger. Two methodologies, stopped-flow kinetic analysis and pulse radiolysis, are fast methods that will measure SOD mimic catalytic behavior. These methods are briefly described in reference 11 and in Section 3.7.2 of Chapter 3. [Pg.270]

This review is concerned with the quantitative aspects of metal-catalysed oxyradical reactions. As such one will find discussions of structures of metal complexes, rate constants and reduction potentials, not unlike our review of 1985 [34], Two areas related to the role of transition metals in radical chemistry and biology have been reviewed recently these are the metal-ion-catalysed oxidation of proteins [35] and the role of iron in oxygen-mediated toxicities [36]. These topics will not be discussed in detail in this review. Related to this work is a review on the role of transition metals in autoxidation reactions [37]. Additional information can be obtained from Afanas ev s two volumes on superoxide [38,39], This subject is also treated in a more general and less quantitative manner by Halliwell and Gutteridge [40],... [Pg.6]


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See also in sourсe #XX -- [ Pg.454 ]




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