Radioimmunoassays competitive

Monodisperse microspheres imprinted with theophylline or 17 (3-estradiol were used in competitive radioimmunoassays showing the MIP s high selectivity for the template molecule. In this case the assay is based on the competition of the target molecule with its radioactively labeled analogue for a limited number of antibody binding sites [77,118]. Figure 15 demonstrates that displacing the radioactively marked theophylline from the imprinted polymer was only possible with theophylline as competitor. Structurally related molecules showed effects solely at elevated concentrations [77]. 

In work similar to that described in Section 20.2.5.10., Haupt and co-workers have found yet another use for their 2,4-D-imprinted polymer [51]. Whereas in the work described above the competing analyte was CMMC (see Fig. 20.14), in these experiments 2,4-dichlorophenoI (DCP) was used as the competitor. This compound is an enhancer of the peroxidase-catalysed chemiluminescence of the well known reaction of luminol and H2O2. Thus, in a certain concentration range, the amount of DCP present in solution is an indicator of the amount of template bound to the MIP. Competitive radioimmunoassays were used to determine the affinity of DCP for the 2,4-D-imprinted polymer and it was found that, while 500 pg of MIP were required to bind 50% of the CMMC, only 250 pg of polymer were required to bind 50% of the DCP. In order to verify this unexpected result, competitive binding assays were performed in the presence of C-2,4-D and it was found that the relative affinities of the polymer for CMMC and DCP were approximately 6 and 10% that of 2,4-D. However, while CMMC bound poorly to the non-imprinted polymer, DCP bound equally as well as to the MIP. This indicates that, in the latter case, binding is almost entirely non-specific. Thus DCP was a poor probe for this system. Fluorescein was also examined as a probe for polymers imprinted with... 

Ricin can be detected in the blood or other bodly fluids of exposed animals using competitive radioimmunoassays or enzyme-linked immunosorbent assays (ELISA). These methods generally do not distinguish between active ricin molecules versus partially degraded or otherwise inactivated toxin. The postexposure time limit for accurate antibody-based detection of ricin in biological samples varies and depends on the route of exposure and the absorbed dose. In the laboratory, ELISA detects ricin in oro-nasal swabs of NHP exposed to ricin aerosol up to 24 h after exposure (Franz and Jaax, 1997). Likewise, ELISA detects ricin in selected tissues of laboratory rats up to 48 h after an i.m. challenge (Leith et al., 1988). 

Serum Albumin Another application of the immunoaffinity chromatography technique was in the analysis of AFBl bound to serum albumin (9). Blood samples were collected on Day 5 from the same individuals who participated in the study described above. Serum albumin was selectively isolated from blood and subjected to enzymatic proteolysis using Pronase. Aflatoxin specific adducts were purified by immu-noaffinity chromatography and quantified by competitive radioimmunoassay. A highly significant correlation of adduct level with AFBl intake (r = 0.69, P less than 0.000001) was observed. From the slope of the regression... 

How does the fish oil alter renal cyclo-oxygenase metabolites Measurements of intrarenal cyclo-oxygenase products by competitive radioimmunoassays show a reduction in PGE2, TXB2 (stable breakdown product of TXA2) and 6-keto-PGFi3j (stable breakdown product of PGI2) in both the renal cortex and medulla . Not only does the fish oil reduce the level of these metabolites but it also promotes the synthesis of approximately 20% of the trienoic series of molecules. ... 

Hgure 1 Simple illustration of the principle of a competitive radioimmunoassay where an antibody is immobilized onto a plate in order to detect the antigen in the test sample. 

Isotyping of monoclonal antibodies 20 Competitive radioimmunoassays 21 Immunoprecipitation of specific antigen 22... 

A competitive radioimmunoassay for the quantification of DAO in lentil seedlings has been reported (Federico et al, 1985). This assay permits the... 

Radiotracers have also been used extensively for the quantitative rnicrodeterrnination of blood semm levels of hormones (qv), proteins, neurotransmitters, and other physiologically important compounds. Radioimmunoassay, which involves the competition of a known quantity of radiolabeled tracer, usually I or H, with the unknown quantity of semm component for binding to a specific antibody that has been raised against the component to be deterrnined, is used in the rnicro deterrnination of physiologically active materials in biological samples (see Immunoassay). 

Radioimmunoassay is a competitive protein binding assay which utilizes an antibody as the binding protein. This assay also employs a highly purified antigen which has been radio-labeled (tagged). 

This equation illustrates the components of a competitive protein binding assay system. That is, the reaction system contains both radioactive and non-radioactive free ligand (P and P) and both radioactive and non-radioactive protein bound ligand (P Q and PQ). This type of assay assumes that binding protein will have the same affinity for the labeled or non-labeled material that is being measured. Although this assumption is not always completely valid, it usually causes no problems of consequence with most radioassays or radioimmunoassays. 

Since the development of radioimmunoassay (RIA), many assays that rely on the specificity of the antigen-antibody binding reaction have been developed because of their inherent sensitivity and specificity. A typical competitive binding... 

The assays that utilize protein instead of antibody are normally termed as competitive protein binding assays. As an antibody is also a protein, therefore, a radioimmunoassay may be looked upon as a type of competitive protein binding assay. 

The radioimmunoassay is based on the evolved competition between the combination of radioactive (Ha+) and nonradioactive (Ha) hapten to the antibody as represented below ... 

Part—VI has been solely devoted to Miscellaneous Assay Methods wherein radioimmunoassay (RIA) (Chapter 32) has been discussed extensively. Various arms of theoretical aspects viz., hapten determinants and purity importance of antigenic determinants and analysis of competitive antibody binding of isotopically labeled compounds. The applications of RIA in pharmaceutical analysis, such as morphine, hydromorphone and hydrocordone in human plasma clonazepam, flurazepam in human plasma chlordiazepoxide in plasma barbiturates, flunisolide in human plasma have been described elaborately. Lastly, the novel applications of RIA-techniques, combined RIA-technique-isotope dilution and stereospecificity have also been included to highlight the importance of RIA in the analytical armamentarium. 

Radioimmunoassay. Radioimmunoassay (RIA) was first described by Berson and Yalow (34) and Luft and Yalow (35). The assay is based upon the competition for an antibody between a radiolabelled antigen and its unlabelled counterpart. The greater the amount of unlabelled antigen in the test sample, the less radiolabelled antigen bound. The concentration of antigen in a test sample can be determined from comparisons with standard curves. 

All radioimmunoassays published thereafter, except those described by Hock and Liemann (38), Freebairn and Crosby (39), and Pohlschmidt et al. (40), were based on a similar procedure (Table 28.2). However, Hock and Liemann (38) applied a more simplified extraction/cleanup procedure for the analysis of chloramphenicol residues in animal tissues, milk, urine, and plasma. In this assay, competitive inhibition between chloramphenicol labeled with " C and antibody has been demonstrated. 

Radioimmunoassay (RIA) is a very sensitive method used to measure minute quantities of an antigen. Since this method is most often used to measure drugs, toxicants, and other xenobiotics, the antigen used to produce the antibody is the small molecule (hapten) linked covalently to a protein. Among the techniques used in the actual measurement, the antigen capture method, in which the competition between radiolabeled antigen and the unlabeled antigen in the sample, is the most common. 

The demonstration that MTs from a wide variety of fish species are recognized by an antiserum raised against one piscine MT has enabled the development of immunotechniques based on ELISA143 and radioimmunoassay (RIA) procedures144 for the quantification of these compounds. A competitive solid-phase assay based on dissociation-enhanced lanthanide fluoroimmuno-detection (DELFI A) of anti-MT monoclonal antibody bound to a solid phase has been reported.145 An electrochemical determination of MTs by square wave cathodic stripping voltammetry has also been developed and optimized.146... 

The most common, but by no means the only or even the most promising, immunochemical assay for small molecules is radioimmunoassay (R1A). As an overview, an immunoassay involves chemically attaching the small molecule of interest (or a derivative of it) to a carrier protein and raising specific antibody titers to it in the serum of an animal. Very dilute antibody solutions are then used to bind the small molecule which has been radiolabeled. The competition of varying known concentrations of unlabeled material is measured and the resulting standard curve used to determine unknown concentrations (Table 1). The steps leading to the development of an R1A are outlined below followed by a description of other immunochemical procedures and an analysis of the attributes and limitations of immunoassay. 

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