Three-component assay

An optical-fiber CL sensor is reported for trichlorethylene assay [87], The sensor consists of a glass fiber bundle and a transducer consisting of three components (i) a gas-permeable membrane to separate trichlorethylene from water, (ii) H2S04-NaN03 mixture as oxidizing agent, and (iii) a luminol solution. The assay of trichloroethylene can be done in the 0.05-0.6- J,g/mL concentration range with a detection limit of 0.03 J.g/mL. 

Figure 13.1 A shows a conventional high performance reversed-phase separation of a three-component mixture of aromatic acid esters obtained with a standard 4.6 mm x 250 mm octadecyl column and methanol water as the eluent. From the view of chromatographic resolution and ruggedness, this is an excellent separation. However, from a practical standpoint, an assay based on this particular separation would not be satisfactory since it wastes large amounts of time between elutions of the individual components.

The % corrected peak areas for HC, LC, and non-main species were plotted against protein sample concentrations and are presented in Figure 11. The % corrected peak area values are shown in Table 3. These results show that the assay is linear for sample concentrations above 0.5mg/mL (Table 3), and that the assay is capable of quantitating all three components with overall %RSDs of 0.8, 1.0, and 11.7% for the HC, LC, and non-main species, respectively. The recommended final protein concentration is 1 mg/mL. 

While the binding of aminoglycosides to the RRE provides a proof of principle, their affinity and, in particular, selectivity traits need to be improved for true therapeutic utility. To facilitate the discovery of potent and selective RRE binders, we developed a solid-phase assay. The components of this assembly include (a) insoluble agarose beads (or microtiter plates) covalently modified with streptavidin, (b) a biotinylated RRE fragment, and (c) a fluorescein-labeled Rev fragment (RevFl). Assembly of the three components generates an immobilized ternary complex whereby the biotinylated RRE binds to the beaded... 

Fig. 2.2. Three components of a typical VS process compound library, virtual assay, and hit follow-up for virtual hits.

Many strategies based on DNA hybridisation assays using AuNPs have been developed. Most of them rely on capturing the NP to the hybridised target in a three-component sandwich format. 

Figure 10.14. Scheme 1 depicts the formation of the three-component sandwich assay discussed in the text. (a) and (b) show flatbed scanner images of microarrays treated with gold nanoparticles before and after silver enhancement, respectively, (c) shows a typical Raman spectrum acquired from one of the silver spots. (d) shows a profile of the Raman intensity at 1192 cm-1 as a function of position on the chip the laser beam from the Raman instrument is moved over the chip from left to right as defined by the line in (b). (With permission from Ref. 40.)... 

Content Uniformity/Assay. The question most often asked is when NIR will be able to be used as a release test. In the earliest NIR assays, tablets and capsules were not analyzed intact. Prior to scanning, the active was extracted and scanned in a clear liquid. The first use of NIR for tablets was reported in 1968. Sherken assayed the meprobamate content in tablet mixtures and commercial preparations. Allen used NIR to analyze a three-component mix carisoprodol, phenacetin, and caffeine. The powder was extracted with chloroform and scanned in the NIR. Several other publications took advantage of the dissolve and scan approach.t ... 

Kajganovic (90) have used Bratton-Marshall reagent for quantitation after separation and elution of sulfonamide mixtures containing sulfacetamide. The solvent system chloroform-methanol-25% ammonia solution (90 15 2.4) gives good separation. The results show a relative standard deviation of about 4%. Sarsunova et al. (86) have used chloroform-ethanol (100 8) as solvent system for the separation of sulfacetamide, sulfathiazole and sulfadimidine in tablets. The sulfonamides are assayed by extraction with acetone-ethanol, separation on alumina, and determination at 270 and 290 nm. The relative standard deviations of 2.5%, 4.1% and 3.2% have been obtained for the three components with six replicates. 

A useful cell-based biosensor should have at least three components living cells as a signal generator upon stimulation, a cell culture component supporting cell growth, and an electrical/optical detection component for signal collection. In addition an assay that connects cell responses to a measurable parameter is necessary if the response itself is difficult to measure. For electrically excitable cells, their electrical activities are indicators for cell status. But for cells with no obvious electrical activity, sometimes a reporter is introduced to translate the cell response to electrical or optical signals. 

Due to the unique nature of the three-component product and the different properties of each, three different assay procedures are required. 

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