Cross-reactivity studies concentration selection

Cross-reactivity was study for similar molecules expected to be present in plasma. L-Cysteine (hydrochloride) and L-methionine at 5 and 4.5 mmol/L, respectively, were assayed in buffer. The observed polarization values correspond to HCY concentrations of 0.0 and 0.1 pmol/L, respectively. Thus, the antibody-binding reaction is sufficiently selective in the presence of these potential interferents. 

In this study, from 957 specimens analyzed, GC-MS results indicate 151 positive and 806 negative results. These are compared with results of the immunoassay methods in Table 16.7. This study concluded that lowering the cannabinoid cutoff concentration from 100 to 50 pg/L THCCOOH increased the percent correct identification of true-positive specimens by all of the commercial immunoassays tested. Therefore, the sensitivities of all of the immunoassays were enhanced, resulting in improved efficiency for these assays. As expected, the specificity decreased slightly when the lower (50 pg/L) cutoff value was used. It is also evident from the results shown in Table 16.7 that there are discrepancies between the results of the eight commercial immunoassays. Preliminary tests suggest that these discrepancies can be attributed to differences in antibody selectivities, since different antibodies are used in the different assays these antibodies may be expected to show different cross-reactivities with other cannabinoid metabolites, as well as other interfering species. 

Method specificity is based on the ability of the selected antibodies to interact exclusively with the analyte, without demonstrable reactivity to other molecules present in the matrix. Specificity is also, in part, dependent on the expected concentrations of cross-reactants in the study sample. For example, an antibody with low cross-reactivity (< 1%) to a compound is unsuitable if the concentration of... 

Atom transfer radical polymerization (ATRP) was selected as an exemplary CRP technique to systematically study the kinetics and gelation behavior during the concurrent copolymerization of monovinyl monomers and divinyl cross-linkers (Scheme 2). The effect of different parameters on the experimental gelation was studied, including the initial molar ratio of cross-linker to initiator, the concentrations of reagents, the reactivity of vinyl groups present in the cross-linker, the efficiency of initiation, and the polydispersity of primary chains. Experimental gel points based on the conversions of monomer and/or cross-linker at the moment of gelation, were determined and compared with each other in order to understand the influence of each parameter on the experimental gel points. 

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