Target chemicals

Toxicity is a relative term and to have any usefulness in designing safer chemicals this concept must be clearly articulated to synthetic chemists. For a chemical to be declared a greener alternative there must be a mechanism for comparing the toxicity of one chemical with another. The hterature contains many references to qualitatively and quantitatively evaluating toxicity that can serve as guidance for characterizing the relative reduction in toxicity for a target chemical (see Table 2.3). ... 

Method validation is needed to demonstrate the acceptability of the analytical method. A recovery test on a chemical being determined should be performed in order to verify the reliability of the series of analyses. Recovery studies are usually conducted by spiking untreated sediment with the target chemical at the deteetion limit, quantitation limit and in the range of 10-50 times the detection limit. The method is considered acceptable when the recoveries typically are greater than 70%. When the recovery is less than 70%, an improvement in the analytical methods is needed. Where this is not possible for technical reasons, then lower recovery levels may be acceptable provided that method validation has demonstrated that reproducible recoveries are obtained at a lower level of recovery. Analysis is usually done in duplicate or more, and the coefficient of variation (CV) should be less than 10% to ensure that recoveries will be consistently within the range 70-110%. 

There are some chemometric (chemometrics is a statistical area which combines statistics and chemistry) tools which use the chemical descriptors and/or fragments of the chemicals used to build up the model, and compare if the chemical descriptors and/or fragments of the target chemical are similar. An example of this approach is given by the freely available software AMBIT. A major disadvantage of this approach is that it is based only on the chemical information. 

The sensors in this section can also be utilized to detect chemicals in liquid through the bulk solution refractive index change induced by the presence of target chemicals. Since no recognition molecules are used, this type of chemical sensing may usually have low specificity. However, these sensors may perform excellently in conjunction with other technologies such as capillary electrophoresis, mass spectrometer, and liquid chromatography in chemical detection. 

Kristensen BK, Bloch H, Rasmussen SK (1999) Barley coleoptile peroxidases. Purification, molecular cloning, and induction by pathogens. Plant Physiol 120 501-512 Kubanek J, Jensen PR, Keifer PA, Sullards MC, Collins DO, Fenical W (2003) Seaweed resistance to microbial attack a targeted chemical defense against marine fungi. Proc Natl Acad Sci USA 100 6916-6921... 

This statement was prepared to give you information about mirex and chlordecone and to emphasize the human health effects that may result from exposure to them. The Environmental Protection Agency (EPA) has identified 1,408 hazardous waste sites as the most serious in the nation. These sites make up the National Priorities List (NPL) and are the sites targeted for long-term federal clean-up activities. Mirex has been found in at least 7 of the sites on the NPL. Chlordecone has been found at 2 of the sites on the NPL. However, neither mirex or chlordecone are on EPA s list of target chemicals and the number of NPL sites evaluated for mirex and chlordecone is not known. As EPA evaluates more sites, the number of sites at which mirex and chlordecone are found may increase. This information is important because exposure to mirex and chlordecone may cause harmful health effects and because these sites are potential or actual sources of human exposure to mirex and chlordecone. 

Once the hapten has been designed and prepared, it is conjugated with a carrier protein to induce the best immunogenicity as possible to elicit an immune response in the animal (most commonly a mouse) in which it is inoculated. The antibodies produced by the defense mechanism of the adaptive immune system that specifically recognizes the hapten are then isolated, overproduced, and purified for testing their catalytic activity toward the targeted chemical reaction. 

Tahlt 1. Target chemical coin/iositions of typical glasses tested at Pacific Northwest National Laboratory... 

Organisms that have a very restricted diet can be expected to have evolved more specific mechanisms to target chemicals in the diet that are especially toxic substances. Thus, an insect living on one plant might protect itself against one toxin by specific biochemical traits—see Chapter 9. 

Application of QSAR and Shape Pharmacophore Modeling Approaches for Targeted Chemical Library Design... 

Oprea, T., Tropsha, A. (2006) Target, chemical and bioactivity databases - integration is key. Drug Discov Today 3, 357-365. 

The lipid membranes are a few nanometers thick. They contain proteins whose role is to actively transport particular target chemicals across these nonpolar barriers. The outer membranes of gram negative bacteria also have protein channels called porins that allow passage of small polar and charged substrates. 

ANALYZER (Reaction-Product). Chemical composition may be determined by the measurement of a reaction product—in an automatic fashion utilizing the basic principles of conventional qualitative and quantitative chemical analysis. Two steps usually are involved in this type of instrumental analysis (1) the formation of a target chemical reaction, and (2) the detennination of one or more of the reaction products. 

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