Biological activity measurements specificity

The radioallergosorbent test (RAST) is a solid-phase sandwich RIA and does not suffer from these general disadvantages that is, it is a direct assay, eliminates nonspecific serum effects, and measures biologically active allergen-specific IgE sandwiched between allergen and Fc-specific anti-IgE antibodies. 

Biological activity The specific ability or capacity of the product to achieve a defined biological effect. Potency is the quantitative measure of the biological activity. 

Specific Activity of Proteins. The specific activity of a protein is defined as the activity of a protein preparation per milligram of that protein. The activity of protein is usually determined as the enzymatic activity, as the ability to bind to a ligand, or as its biological activity. The specific activity of a protein increases with the increase in the purification of a protein. There are several methods to determine the amount of protein in a preparation. The simplest way is to measure the absorption at 280 nm of light. In addition, several colorimetric methods are available, of which the Lowry method and the Bradford method are commonly used (see Bell and Bell 1988). 

Where applicable, a description of the potency test or tests for measuring biological activity, including specifications for potency determination... 

The proof of activity of a biological pesticide is typically evaluated by a standardized bioassay except in the case of microbial metabolites where the major active ingredient(s) may be measured by analytical methods. Biological activity measurements, besides serving as a parameter for quality control, are an essential tool in the product development and optimization process. It is important to define the assay procedure in order to compare production batches and experimental formulations. These assays are typically used for product release or may be designed to assess specific aspects of product activity such as mobility in soils, colonization on leaf surface, etc. 

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. 

SAMs was correlated to the affinities of the Fn-specific monoclonal antibodies. Although antibody-based measurements could not distinguish between conformational (structural) and orientational changes in the adsorbed proteins, they provided information about the biological activity of adsorbed proteins. 

Potentiometric stripping analysis has been applied by Sheffrin and Williams [320] to the measurement of copper in seawater at environmental pH. The advantage of this technique is that it can be used to specifically measure the biologically active labile copper species in seawater samples at desired pH values. The method was applied to seawater samples that had passed a 0.45 pm Millipore filter. Samples were studied both at high and at low pH values. 

Sharama et al. [479] compared results obtained in the determination of cobal-amins in ocean waters by radioisotope dilution and bioassay techniques. These workers showed that the isotopic methods measured both biologically active and inactive cobalamins indiscriminately when porcine factor was used as the B12-specific binder. 

AUC and Cmax are commonly measured to identify safety ratios for new chemical entities. Since the analytical methods used for biotechnologically derived pharmaceuticals may lack specificity, a clinical marker of biological activity or efficacy may sometimes be more appropriate than exposure data. 

The quantitation of a protein that has a specific biological function, a hormone, for instance, may not give a true indication of its biological activity owing to the inactivation of some of the protein. For proteins that have definite biological functions the choice is between chemical quantitation and bioassays. For this reason the catalytic activity of an enzyme is more frequently measured than is its protein concentration. 

Many biopharmaceutical preparations are heterogeneous and may be difficult to fully characterise. Certain fractions of a preparation may have different biological activity or kinetics than the intended product. It is important that such fractions are appropriately qualified. The proportions of these fractions may be altered when production changes are made or they may be different between similar products produced by different manufacturers. Because of their proteinaceous nature and their novel mechanisms of action, all preclinical and clinical development steps must be re-evaluated. For pharmacokinetic studies, blood concentrations should be measured by specific analytical techniques (most often ELISA), which quantify the active protein and not one of its fragments or inactive forms, such as antigen-antibody complexes. For PK-PD studies of monoclonal antibodies, relevant biomarkers are most often circu-... 

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