Relative specific response

If the detector response is linearly proportional to the concentration of solute in the column effluent, there is also a linear proportionality between the peak area and the total mass of solute in the eluted chromatographic zone. Hence, for the peak areas of the compound under determination, i, calibration standard s and the reference compound r (cf., the definition of the relative specific response), Ai, As andAr, respectively, we have... 

The apparatus constant can be eliminated by using the so-called relative specific response the relative specific response of a compound is the ratio of the specific responses of the compound and of a deliberately chosen reference compound (r). Hence, the relative specific responses of the compound under determination and of the calibration standard,7 // and/ (cf., eqns. 12—14), respectively,are... 

The relative specific response characterizes unambigously the specificity of detection (with a given detector and under given conditions) and is relatively little dependent on the variations in instrumental parameters (cancellation of the apparatus constant). Therefore, the relative specific response is the most suitable basis for the definition of the mass-specific response factor. This factor can be defined as the inverse of the relative specific response hence, for compounds i and s we have... 

The ability to reduce stimulus-response mechanisms to single mono tonic functions allows relative cellular response to yield receptor-specific drug parameters. 

The distinction between detection and identification is important, since it may affect the overall response time and options. A detection occurs when a chosen parameter exceeds its threshold value. The detection may be nonspecific—that is, it registers the occurrence of an anomaly but does not necessarily indicate the presence of a particular threat substance. By contrast, identification establishes the identity of the threat substances in a given set. Nonspecific detection systems may have a relatively rapid response time compared with that of specific identification systems, but the former typically provide a lower confidence level that a threat substance is in fact present. In some cases, an alarm from a rapid but nonspecific detection system may be used... 

NPD (FTD) Relatively high sensitivity Specific response Smaller dynamic range than FID Susceptible to operating conditions [31]... 

The dissimilar multiprotein complexes, ALP-Fab and ALP-E3-Fab , were similarly purified over an octyl-Sepharose column. The protein fractions eluted from this column were characterized relative to the effective protein concentrations required to generate a specific response equivalent to that of ALP-Fab. These results show (Table 19.4) that the more hydrophobic protein fraction... 

Another difficulty in the gas chromatographic separation of amino acids is the choice of detector and it may be necessary to split the gas stream and use two different detectors. The flame ionization detector, which is commonly used, is non-specific and will detect any non-amino acid components of the sample unless purification has been performed prior to derivatization. In addition the relative molar response of the flame ionization detector varies for each amino acid, necessitating the production of separate standard curves. As a consequence, although gas chromatography offers theoretical advantages, its practical application is mainly reserved for special circumstances when a nitrogen detector may be useful to increase the specificity. 

Polarographic probes that respond specifically to concentrations of Oj, CO2 or SOj are very useful. They have decided advantages over the more clumsy manometric monitoring. Their use is limited to slow reactions or the continuous-flow approach, because of the relatively long response time of the probe. An 02-eleetrode system for incorporation in a spectrophotometer cuvette, for simultaneous monitoring of [Oj] and spectral changes, has been deseribed. 

Exposure. Exposure to 1,3-DNB is currently measured indirectly by determining levels of methemoglobin in the blood (Donovan 1990). However, increased methemoglobin formation is not a specific response to 1,3-DNB exposure and may occur after exposure to other nitrobenzene compounds such as the other two isomers of dinitrobenzene. Determination of methemoglobin levels is widely used and is a reliable detection method. Very few methods are available for direct evaluation of 1,3-DNB levels, and they are not extensively used, probably because of the relatively rapid rate of conversion of 1,3-DNB to its degradation products (Cossum and Rickert 1985). Preliminary data suggested that the formation of adducts of 1,3,5-TNB with tissue DNA and/or with blood proteins may be useful as markers for exposure to 1,3,5-TNB (Reddy et al. 1991). Further research with both 1,3-DNB and 1,3,5-TNB in the area of adduct formation could provide valuable additional information. 

Moreover, the sensitivity of biosensors containing Sphingomonas sp. or Pseudomonas fluorescens allowed the specific determination of the polycyclic aromatic hydrocarbon (PAH) naphthalene, although both biosensors showed relatively high responses to salicylate and acetate [117]. However, the remarkably low limit of detection obtained by these biosensors of 10 pg 1" naphthalene was not sufficient for the monitoring of drinking water, due to the prescribed upper limit for the concentration of PAH in drinking water of 0.2 pg 1". ... 

The results in Table I show that, in the presence of plant material, the standard GA3 is spread over a considerably wider range than is usual. However, after the sample is further purified by the second run, the mobility of GA3 returns to normal. The same pattern of distribution, with zone III as maximum, is manifest in the natural run, although at considerably lower fluorescent intensities. For both fractions, the presence of GA3 is confirmed by the capryl system. A portion of zone III of the natural extract gave positive response proportional to concentration in the pinto bean seedling assay and in the dwarf maize mutants I and V assay. The relative activity on both mutants was approximately equal, as is required for GA3 (26). The correlation of relatively specific biological growth activity with chromatographic and chemical behavior affirms the presence of a GA3-like substance in kudzu vine. 

Figure 273 Cationized BSA even can increase the specific antibody response to large proteins coupled to it. This graph shows a comparison of the relative antibody response in mice to injections of ovalbumin, either in an unconjugated form or conjugated to native or cationized BSA. The quantity injected was standardized according to the amount of ovalbumin present. The highly basic cBSA molecule modulates the immune response to enhance the production of antibodies toward even proteins conjugated with it.

PC2 may also function as an intracellular Ca2+ channel itself. A large population of PC2 channels can be detected in the endoplasmatic reticulum (Vassilev, Guo et al. 2001 Koulen, Cai et al. 2002 Giamarchi, Padilla et al. 2006). Until recently, it was thought there were only two major classes of intracellular Ca2+ channels the RyRs and the InsP3Rs. It is now agreed that there are three classes of intracellular channels. Many cell types contain all three classes of channels, but the relative densities vary dramatically. Cells also can have multiple isoforms of these channels. The co-existence of a variety of intracellular channels is not surprising as cells need to respond to diverse stimuli with specific responses. Whether the intracellular function of PC2 channels is relevant for the disease mechanism of PKD remains to be established. 

The existence of different varieties of cholinergic receptors is important pharmacologically. Some drugs are relatively specific for a certain cholinergic receptor subtype, whereas others tend to bind rather indiscriminately to all cholinergic receptors. Obviously, specific drugs are preferable because they tend to produce a more precise response with fewer side effects. As this chapter will point out, however, specificity is only a relative term, and drugs that bind... 

Mechanism of Action. Cyclosporine and tacrolimus (see below) are known as calcineurin inhibitors because they inhibit a specific protein (calcineurin) in lymphoid tissues. This inhibition ultimately suppresses the production of IL-2, a cytokine that plays a critical role in immune response by promoting the growth and proliferation of activated T lymphocytes and other immune cells, such as NK. cells (see Fig. 37—1).5,52 Thus, cyclosporine is one of the premier immunosuppressants because of its relative selectivity for T cells and its inhibition of a key mediator of the immune response (IL-2).41 This relatively specific inhibition is often advantageous when compared with other nonse-lective drugs such as azathioprine, cyclophosphamide, and glucocorticoids that inhibit virtually all the cells and chemical mediators involved in the immune response. 

Nussbaum MA, Baertschi SW, Jansen PJ. Determination of relative UV response factors for HPLC by use of a chemiluminescent nitrogen-specific detector. J Pharm Biomed Anal 2002 27 983-993. 

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