Biomedical Engineering Reference
In-Depth Information
Fig.3. Principle of a sandwich TELISA
ing ofconjugates.But basic research on TELISA systems has been oftremendous
importance for future immunosensors including fluorescence assays.
3.3
Determination of Enzyme Activities
In bioprocess monitoring,medicine and downstream processing,the analysis of
enzyme activities is of tremendous importance. In mammalian cell cultures,
lactate dehydrogenase activity informs us about the state of the cell; enzyme
activities in blood, inform physicians about the patient's health; and in down-
stream processing, several biochromatographic procedures are monitored via
enzyme activity analysis.After a simple modification,the ET can be adapted for
these applications. Here, sample aliquots are mixed directly in front of the
thermistor with a buffer containing substrate .Again,the resulting heat provides
information about the concentration (i.e.enzyme activity).The technique can
be used for enzyme activities up to 0.01 units/ml (Danielsson and Larsson,
1990). Danielsson et al. (1981b) demonstrated this procedure by monitoring
chromatographic purifications of enzymes.Here,enzyme activity is measured
at the efflux of a chromatographic column.Experiments were carried out with
ionic-, gel-, and affinity chromatography to separate lactate dehydrogenase,
glucose-6-phosphate dehydrogenase and hexokinase (see Table 4).
In another procedure,substrate or product concentration is analyzed after an
enzymatic conversion has taken place.The method extends the possibilities of
analysing enzyme activities. For instance, arginase cleaves buffer-containing
arginine to urea and ornithine.Therefore,the ET determines arginases activity
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