Biological activity measurements sensitivity

The method appears to be highly specific, with an index of precision of 0.044 (19 assays). It is also sufficiently sensitive for assaying circulating levels of the hormone. In samples taken over the entire menstrual cycle, the biological activity measured by this assay was consistently 5.5 times that recorded by immunoassay. 

Selection of one or more species sensitive to the endpoint being measured, for example, infections or pathologic sequelae and/or biological activity or receptor binding. 

Because several of the metabolites of vitamin D3 are biologically active, the molecular species of vitamin D3 which passes into the yolk cannot be determined just from measurement of antirachitic activity. Consequently, a reliable and sensitive method for determining the amount of the unchanged form of vitamin D3 would be extremely beneficial to those interested in the metabolism and other factors that influence the chicken to deposit vitamin D3 in... 

Once it was established that pheromone biosynthesis was regulated by a peptide produced in the SEG, the next goal was to identify the peptide. In the purification of any biologically active factor, each purification step requires a sensitive bioassay to measure the active material. In the purification of PBAN, the bioassay consisted of head ligated females that were injected with bioactive fractions. After a 1-3 h period of incubation, the pheromone gland was excised and titers of pheromone determined by gas chromatography (GC). The first PBAN was purified and identified from H. zea (Raina el ah, 1989). Dissection of about 5000 brain-SEG complexes followed by several steps of HPLC purification resulted in a pure peptide that could be sequenced. It was found to be a 33 amino acid peptide with a C-terminal amide (Table 5.1). The peptide was synthesized and was shown to be active in the bioassay in a dose as low as 2 pmol (Raina et al., 1989). In the same year, a PBAN from B. mori was purified and sequenced (Kitamura et al.,... 

The availability of sensitive analytical tests to adequately characterize a product and to measure the predicted possible changes is central to a comparability assessment. Obviously tests should be chosen that will be the most likely to detect important changes. ICH Q6B offers advice on physicochemical, biological activity, and immunochemical properties, purity (impurity), con-... 

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