Enzyme-linked immunosorbent assay,

Enzyme-linked immunosorbent assays (ELISA) are by far the most common immunological assay used in biochemical and clinico-chemical laboratories (Crowther 1995). The method is just as specific as RIA and it can achieve comparable sensitivities under optimal conditions. It can be carried out in various ways, but the common feature is that detection relies on turnover of a chromogenic substrate by an 

A mix of known concentrations of the radio-actively labelled antigen (tracer) and an unknown concentration of the unlabelled antigen are incubated with the antigen-specific antibody. On addition of an anti-antibody, which leads to the precipitation of the antibody-antigen 

In competitive ELISA, the procedure used is very similar to that described above for RIA the antigen coupled to the enzyme is bound to an antibody immobilised on 

ABTS (2,2 -azinobis[3-ethylbenzthiazolin-6-suIphonate]) whose turnover is monitored photometrically. The detection limit of this assay is about 5 pg ml-1. 

The sensitivity of ELISA can be further increased by coupling to a second enzyme reaction. For example, the alkaline phosphatase reaction can be used to convert NADP+ into NAD+, which in the presence of a dehydrogenase can be used to convert a leuco-dye into coloured product. 

ELISA utilizes complex ( sandwich-type ) and highly specific interactions between immobilized antibody and antigen (microorganism) present 

Antibody present in liquid binds to the antigen.The plate is washed. 

Another component that binds to the antibody but also contains a specific enzyme is added.The plate is washed. 

Substrate for the attached enzyme is added. If enzyme is present, a colored product will be formed indicating the presence of the antibody. 

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An enzyme-linked immunosorbent assay (eflsa) has been developed for the detection of residues on hands. As Httle as 50 pg of TNT can be detected (126). Liquid chromatography/thermospray negative-ion tandem ms has been successfully used to detect picogram levels of explosives in post-blast debris (127). 

MacroHdes are obtained by controUed submerged aerobic fermentations of soil microorganisms. Although species of Streptomjces have dominated, species of Saccharopoljspora Micromonospora and Streptoverticillium are also weU represented. New techniques such as enzyme-linked immunosorbent assay (ELISA) based assays may prove beneficial for discovering new stmctures (464). 

In each of the assays of potency the amount of the immunoglobulin and the amount of a corresponding standard preparation that are required to neutralize the infectivity or other biological activity of a defined amount of virus or to neutralize a defined amount of a bacterial toxin are determined. The two determined amounts and the assigned unitage of the standard preparation are then used to calculate the potency of the immunoglobulin in International Units (lU). ELISA, enzyme-linked immunosorbent assay. 

HPLC, high-petfomtance liquid chromatogtaphy ELISA, enzyme-linked immunosorbent assay method RIA, radioimmunoassay method. 

Several heterogeneous electrochemical enzyme immunoassays have been demonstrated. These are based on the enzyme-linked immunosorbent assay (ELISA) technique... 

ELISA Enzyme-linked immunosorbent assay EMS Eosinophilia-myalgia syndrome ENS Enteric nervous system EO Eosinophil... 

Morishita, N., Kamiya, K., Matsumoto, T., Sakai, S., Teshima, R., Urisu, A., Moriyama, T., Ogawa, T., Akiyama, H., and Morimatsu, F. (2008). A reliable enzyme-linked immunosorbent assay for determination of soybean proteins in processed foods. /. Agric. Food Chem. 56, 6818-6824. 

H.A. Moye, Enzyme-linked immunosorbent assay (ELISA), in Pesticide Residues in Foods Methods, Techniques, and Regulations, W.G. Fong, H.A. Moye, J.N. Seiber, and J.P. Toth (eds), Wiley, New York, Chapt. 6 (1999). 

Watanabe et al. developed an enzyme-linked immunosorbent assay (ELISA) for the detection of inabenfide, a plant growth regulator, in rice. Specific monoclonal antibody (MAB) is used for this method. The effects of rice matrices on the sensitivity of ELISA can be reduced by adding 0.1% Tween 20. Good reproducibility and accuracy of the proposed ELISA were obtained for rice samples and the recovery was 92% at a fortification level of 5-500 xgkg . ... 

The need to understand the fate of pesticides in the environment has necessitated the development of analytical methods for the determination of residues in environmental media. Adoption of methods utilizing instrumentation such as gas chro-matography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS), liquid chromatography/tandem mass spectrometry (LC/MS/MS), or enzyme-linked immunosorbent assay (ELISA) has allowed the detection of minute amounts of pesticides and their degradation products in environmental samples. Sample preparation techniques such as solid-phase extraction (SPE), accelerated solvent extraction (ASE), or solid-phase microextraction (SPME) have also been important in the development of more reliable and sensitive analytical methods. 

TR. Dombrowski, E.M. Thurman, and G.B. Mohrman, A first application of enzyme-linked immunosorbent assay for screening cyclodiene insecticides in ground water, in Environmental Immunochemical Methods, ed. J.M. Van Emon, C.L. Ger-lach, and J.C. Johnson, American Chemical Society, Washington, DC, pp. 148-154 (1996). 

Muldoon et al. developed a monoclonal-based competitive inhibition enzyme-linked immunosorbent assay (cELISA) for sulfadimethoxine. The group compared... 

EIAs are more desirable for the measurement of agrochemicals than enzyme-linked immunosorbent assays (ELISAs) for several reasons. EIAs are easier to run, require minimal liquid transfers, and are completed in brief time frames, approximately 40 min for tube assays to 2.5 h for microtiter plate assays. In contrast, ELISAs are more complex, have many steps involving transfer of reagents, and require 6-8 h to complete. Most commercially available immunoassays utilize the EIA format. 

Enzyme-linked immunosorbent assay (ELISA). Li and Li developed an ELISA procedure for imidacloprid to determine its residues in coffee cherry and bean extracts. A 25-g amount of sample extracted with 300 mL of methanol and 1% sulfuric acid (3 1, v/v) for 3 min. An aliquot of the sample extract (0.5 mL) is mixed with 1 mL of water and a gentle stream of nitrogen is used to evaporate methanol. The solution is then extracted with 1 mL of ethyl acetate, the extract is reconstituted in 1 mL of PBST (phosphate-buffered saline containing 0.05% Tween 20) and competitive ELISA is performed to quantify imidacloprid in the extract. Eor methanol extracts of coffee cherries and beans fortified with imidacloprid at 0.5 mgL recoveries of imidacloprid by the ELISA method were 108 and 94, respectively. 

Oxime carbamates are not directly amenable to gas chromatography (GC) because of their high thermal instability, which often leads to their breakdown at the injection port or in the column during analysis. Analysis of oxime carbamates by GC with sulfur detection or flame photometric detection involves oxidation of the intact insecticides or alkaline hydrolysis to form the more volatile but stable oxime compound. Enzymatic techniques have been reported for the analysis of these compounds. Enzyme-linked immunosorbent assay (ELISA) has been used to determine aldicarb and its sulfone and sulfoxide metabolites and methomyl in water, soil, and sediment samples. 

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