Detoxifying

Nucleophilic substitution is one of a variety of mechanisms by which living systems detoxify halogenated organic compounds introduced into the environment Enzymes that catalyze these reactions are known as haloalkane dehalogenases The hydrolysis of 1 2 dichloroethane to 2 chloroethanol for example is a biological nude ophilic substitution catalyzed by a dehalogenase... 

Microbial processes can also detoxify mercury ions and organic compounds by reducing the mercury to the elemental form, which is volatile (86). This certainly reduces the environmental impact of compounds such as methylmercury, however, such a bioprocess would have to include a mercury capture system before it could be exploited on a large scale with pubHc support. 

Cytochrome P-450 is frequently the oxygenase which detoxifies xenobiotics, including herbicides. Blocking the metaboHsm of a herbicide increases the activity or delays the inactivation, thus increasing the effectiveness of such herbicides as chlortoluron [15545-48-9] and bentazon [25057-89-0]... 

DHBs after absorption distribute rapidly and widely among tissues but bio accumulation is low (121). They are metabolized to their respective benzoquinone and then detoxified by conjugation and excreted in the urine mainly as conjugates. Some deconjugations may occur in the urine. Resorcinol is also excreted in the urine in a free and conjugated state, essentially glucuronide and sulfate. 

Pyrethroids from Chiysanthemic Acid. The unsaturated side chains of the aHethrolone alcohol moieties of the natural pyrethrins are readily epoxidized by microsomal oxidases and converted to diols, thus detoxifying the insecticides. Esterification of chrysanthemic acid (9), R = CH3, with substituted ben2yl alcohols produces usehil insecticides barthrin [70-43-9J, 2-chloro-3,4-methylenedioxyben2yl (+)-i7j ,/n7 j -chrysanthemate, and dimethrin [70-38-2] 2,4-dimethylben2yl (+)-i7j ,/n7 j -chrysanthemate. These have alimited spectmm of insecticidal activity but are of very low mammalian toxicity, ie, rat oralLD s >20,000 mg/kg. 

Water Treatment Compounds. Like the disinfecting agents, several water treatment compounds are used in aquaculture. Of particular interest is potassium permanganate which is exempted from registration by EPA when used as an oxidizer or detoxifier and can control certain parasites, external bacteria, and possibly fungi (9). 

Barium metal and most barium compounds are highly poisonous. A notable exception is barium sulfate which is nontoxic because of its extreme iasolubihty ia water. Barium ion acts as a muscle stimulant and can cause death through ventricular fibrillation of the heart. Therefore, care must be taken to avoid contact with open areas of the skin. Workers must wear respirators (of type approved for toxic airborne particles), goggles, gloves, and protective clothing at all times. The toxic barium aluminate residue obtained from barium production is detoxified by reaction with a solution of ferrous sulfate and converted iato nontoxic barium sulfate. According to OSHA standards, the TWA value for Ba and Ba compounds ia air is 0.5 mg/m. ... 

A castor meal treating program for simultaneous detoxification and deaHergenation led to the development of a process to detoxify the meal by heat and moisture and to deaHergenate by chemical and water treatment utilizing expander/extmder processing techniques (14). This detoxified and deaHergenated castor meal is safe to use as feed for animals (see Feeds and feed additives). 

If the primary intent is to detoxify the waste, then the characteristics of the waste which make the waste... 

The thermal processes applicable to detoxify organics in a solid/sludge matrix include the following incinerators ... 

Most treatment options for detoxifying the hazardous constituents from RCRA facilities must have a uniform feed to the process. However, the media in which hazardous constituents are located are not generally homogeneous. Thus, some form of pretreatment of the waste or waste medium will probably be required to prepare the waste for further treatment by chemical, biological or thermal means. 

Livingston, A.G., Extractive Membrane Bioreactors A New Process Technology for Detoxifying Industrial Waste waters, J. Chem. Tech. Biotech., v.60, pp. 117-124, 1994. 

Bioremediation- Use of microorganisms to remove or detoxify toxic or unwanted chemicals from an environment. 

In this scheme, OELs should be a dose somewhere between compensatory effects, in which the organism is able to detoxify, metabolize, or excrete the substance, and early impairment. Although there may be profound differences of opinion as to what constitutes this dose, this approach leads to the conclusion that available scientific data permits identification of a clear threshold dose below which exposure to the substance in question is not expected to lead to adverse effects. 

The methyl ether obtained from detoxifying perfluoroisobutene is dehydro fluorinated with alkali Fiydrolysis ol the resulting vinyl ether yields hexafluo-roisobutanoic acid [17] (equation 18)... 

It is now apparent that bacteria have developed resistance to heavy metals and the detoxifying process is initiated and controlled by metallo-regulatory proteins which are able selectively to recognize metal ions. MerR is a small DNA-binding protein which displays a remarkable sensitivity to Hg +. The metal apparently binds to S atoms of cysteine and this has been a major incentive to recent work on Hg-S chemistry. 

Natural herbicides produced by microorganisms have had a profound influence on world agriculture. Many species of higher plants have survived the ages because of their ability to detoxify or avoid the toxic effects of these compounds, and extensive effort has gone into the commercial breeding of other species to develop these abilities. Still, the structural variety of natural herbicides appears to be so great that their effects are still of major concern in food production. 

On pharmacodynamic grounds, tumor resistance may be caused by such diverse mechanisms as the mutation or redundancy of topo II, the overexpression and preferred nuclear localization of proteasome a-type subunits (leading to a anomalous degradation of topo II), genetic deletion or loss-of-function mutations of p53, overexpression of ROS-detoxifying enzymes, overexpression of Bcl-2 (leading to a diminished cyt c release), etc. However, none of these factors would universally predict the development of anthracycline-resistance in a given tumor or another. 

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