Radioactive tagging

Surface Area. Overall catalyst surface area can be determined by the BET method mentioned eadier, but mote specific techniques are requited to determine a catalyst s active surface area. X-ray diffraction techniques can give data from which the average particle si2e and hence the active surface area may be calculated. Or, it may be necessary to find an appropriate gas or Hquid that will adsorb only on the active surface and to measure the extent of adsorption under controUed conditions. In some cases, it maybe possible to measure the products of reaction between a reactive adsorbent and the active site. Radioactively tagged materials are frequentiy usehil in this appHcation. Once a correlation has been estabHshed between either total or active surface area and catalyst performance (particulady activity), it may be possible to use the less costiy method for quaHty assurance purposes. 

This example assumes that RIA was chosen. The principle behind RIA is the competition between the analyte A and a radioactively tagged control C (e.g., a /-marked ester of the species in question) for the binding site of an antibody specifically induced and harvested for this purpose. The calibration function takes on the shape of a logistic curve that extends over about three orders of magnitude. (Cf. Fig. 4.38a.) The limit of detection is near the B/Bo = 1 point (arrow ) in the upper left corner, where the antibody s binding sites are fully sequestered by C the nearly linear center portion is preferrably used for quantitation. 

Macroarrays [7] Probes are spotted onto nylon, plastic or nitrocellulose solid matrix 8cm by 12cm with approximately 200 to 5000 genes Radioactivity tag labeling phosphorimager detector Passive Clontech Laboratories, Research Genetics... 

In 1987, CL started to be applied in DNA hybridization assays as an alternative to the use of radioactive tags. These assays are based on the specificity of a binding process that of DNA strands for each other. An unknown DNA can be identified with the Southern blot method in which the strands of the analyte are separated and allowed to interact with labeled probe DNA strands on nitrocellulose filter paper. If the label on the probe is detected, the DNA can be identified and, in some cases, quantitated. Conventionally, radioactive tags were used be-... 

Many methods have been proposed for determining the efficiency,/ of the initiator. The most direct method depends on a quantitative assay of the polymer for initiator fragments, and its comparison with the amount of initiator decomposed. This is not difficult in those cases where the initiator leaves a reactive endgroup on the polymer or is radioactively tagged. 

Perkin-Elmer LS-2B microfilter fluorometer Fluorescence is used in immunochemistry. Essentially the radioactive tag on the antigen is replaced by a fluorophore. The most commonly used tags are fluorescein and umbelliferone. 

Mucus flows in the bronchial airways have not been directly measured. The measurements of particle clearance for radioactively tagged particles depend on a mixture of deposition sites and mucus flow rates. However, such measurements have shown reproducibility in the individual and a large variation among individuals. ... 

Kinetic study of this reaction usually requires sampling the polymerizing mixture and analyzing for the concentrations of the various reaction species at different polymerization times. Vofsi and Tobolsky in 1965 reported the use of radioactively tagged initiator (10), while Saegusa amd coworkers in 1968 developed a "phenoxy end-capping" method in which the oxonium ion is trapped with sodium phenoxide and the derived phenyl ether at the polymer chain end quantitatively determined by UV spectrophotometry (11). 

Figure 10.5. Upon transformation, cancer cells often express unique surface antigens termed tumour surface antigens (TSAs). Antibodies raised against these will selectively bind the tumour cells. The antibody used may be unconjugated or conjugated to a drug, toxin or radioactive tag...

Several clinical trials have evaluated (or continue to evaluate) monoclonal antibodies to which a radioactive tag has been conjugated. These are usually employed as potential anti-cancer agents. The rationale is selective delivery of the radioactivity directly to the tumour site. Most of the radioisotopes being evaluated are /i-emitters these include I and I (iodine), Re and Re (rhenium) and (yttrium). The medium-energy radioactivity these emit is capable of penetrating... 

There are several immunological techniques in use. Enzyme multiplied immunological technique (EMIT) employs an enzymatic reaction to determine concentration, whereas radioimmunoassay (RIAl uses radioactively tagged reagents such as I lu measure concentration. 

Oral administration of bromelain to rats resulted in an increase in proteolytic activity in blood [82]. Seifert et al, [S3] administered radioactive bromelain via the duodenum to rata. They proved that 40% of the radioactively tagged bromelain was absorbed in its high molecular weight form in blood and lymph. The enzyme was identified using anti bromelain antiserum raised in rabbits. They claimed that a proteolytic enzyme of about 28,000 daltons passed into the blood and then exerts its physiological action [84]. 

If the sample is radioactively tagged, it can be quantitated with one of the radioscanning devices. Reference 21 provides more details of all the scanners, including photographs of them. 

An important factor in the interaction of foreign surfaces with blood is the rapid adsorption of plasma proteins onto such surfaces when they are exposed to blood (4). For this reason the adsorption of radioactively tagged blood components on heparinized and unheparinized surfaces was measured. Proteins were dissolved in approximate physiological concentrations in a buffered (pH 7.35) physiological saline solution and the solutions were exposed to the test surfaces for 2 hours at 37 °C. in a static system. After the exposure, the surfaces were rinsed with physiological saline and distilled water and then dried. The amount of protein on the surfaces was determined in a 27r-gas flow proportional counter (7). As shown in Table III, although both heparinized surfaces were nonthrombogenic, there is no consistent pattern of either increased or decreased adsorption of the proteins caused by the heparinization. In-... 

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