Biological activity measurements precision

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. 

The determination of biological activity is always associated with some experimental errors, which may be caused by variability of biological objects, inaccuracy of measurements due to the limited precision of the used equipment, inaccuracy of the personnel doing manual and mental work. 

The major drawback of these techniques is their lack of specificity, poor precision (CV = 15% to 100%), and long analysis time (1 to 4 days). Their main advantages are that they measure biologically active molecules and detect as little as O.lpg/mL. 

Although insulin has been assayed for more than 40 years, there is no highly accurate, precise, and reliable procedure available to measure the amount of insulin in a patient sample. Many insulin assays are commercially avaEable. The techniques most widely used in the United States are immunochemical. Bioassays, although of greater physiological relevance because they measure biological activity, are labor intensive and not widely used. A stable isotope dEu-... 

The ultimate goal of an assay or an analytical procedure is to measure accurately a quantity or a concentration of an analyte, or to measure a specific activity, as in some assays for biomarkers. However, many activity assays, such as cell-based and enzyme activity assays, may not be very sensitive, may lack precision, and/or do not include the use of definitive reference standards. Assays based on measurements of physicochemical (such as chromatographic methods) or biochemical (such as ligand-binding assays) attributes of the analyte assume that these quantifiable characteristics are reflective of the quantities, concentration, or biological activity of the analyte. For the purpose of bioanalytical method validation, we will follow the recently proposed classifications for assay data by Lee et al. [4,5]. These classifications, as summarized below, provide a clear distinction with respect to analytical validation practices and requirements. 

The RMA have been shown to be simple, sensitive, and specific for the measurement of vitamin B12, folate, and niacin in the blood and for the measurement of vitamin B12 and folate in food. Further work will be carried out for the measurement of niacin in food. For the determination of the biologically active forms of niacin, the RMA is more specific than the TMA. The RMA is also more specific than the CPBA for the measurement of vitamin B12. The advantages of the RMA over the TMA are (i) it is sensitive and simple (ii) the colored or turbid materials do not interfere with the assay (iii) only small amounts of material are required and most important, (iv) RMA combines the biological specificity of the microorganisms with the precision of measuring radioactive decay as the endpoint. 

Bioassays are frequently used as an alternative or in addition to immunoassay techniques. Bioassays, in contrast to immunoassays, quantify not the pharmacologically active substance, but its biological activity, for example, in cell culture models based on cell differentiation, cell proliferation, or cytotoxicity as well as gene expression assays or whole animal models. Frequent major problems with bioassays comprise a high variability in the measured parameters, lack of precision, and their time- and labor-intensive performance. Furthermore, bioassays oftentimes also lack specificity for the measured compound, as they may also detect the response to bioactive metabolites [16,17]. 

Perhaps the most obvious way to characterise different chemical structures is to use experimental measurements of some characteristic properties, such as melting point, boiling point or refractive index for example. This approach has the advantage that these properties are unambiguously and easily defined and in many cases easily measured to any desired precision. Solubility is clearly an important factor in the biological activity of any compound, and indeed this was found to be one of the earliest successful molecular descriptors, where toxicity... 

Information for the description of the receptor are given as a set of experimental biological activities, Ai, corresponding to molecules Mi, i = 1,N. It is supposed that the biological activities are measured in the same conditions for all the M compounds, with the same accuracy and precision. 

MEMS-Based Acoustic Wave Biosensors Introduction A MEMS-based acoustic wave biosensor is a chemical sensor which detects changes in resonant frequency of a mechanical resonator when biomolecules are adsorbed on the surface of a biologically active membrane. Since frequency change can be measured very precisely, very small mass changes can be measured. This leads to high sensitivity of the biosensors. Typical acoustic wave biosensors are bulk acoustic wave (BAW) and surface acoustic wave (SAW) sensors. 

ENDOR methods can be especially useful for investigating biological systems because powder-type spectra can yield isotropic and anisotropic coupling constants with a higher resolution and precision than can conventional ESR spectroscopy. Typical examples are the radical ions occurring as primary photoproducts in reaction centers of photosynthetic bacteria. Liquid-state ENDOR measurements have been made on biologically active organic species such as the vitamin quinones. 

Of paramount importance are the two crossover phenomena observed in protein hydration water, which, on the basis of the many results we have described, can be considered responsible for the biological activity of macromolecules, including RNA and DNA. Neutron measurements of the MSD indicate, surprisingly, that the crossover temperature of biopolymer and its hydration water are closely synchronized. More precisely, FTIR experiments indicate that when a biosystem restores its dynamics, the solvent crosses from a strong to a fragile liquid, that is, the HB networking changes from a thermal state in which LDL dominates to one in which HDL dominates. At the same time, irreversible denaturation takes place when the HB numbers decrease to the point at which only a few water molecules are bonded. 

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