Analytical applications of bioluminescence--a matter of proper kinetic design and recording.

The way bioluminescence analysis employs photometric technique is illustrated in relation to the resulting demands on signal processing and detectability. The analytical reaction may be regarded as composed of a supply reaction providing the excited species followed by a decay reaction in which light is emitted. Bioluminescence analysis implies the recording of a velocity, hence rate regulation forms the basis of the development of an analytical set-up. In principle two means of design are used, either the application of a pulse technique or the monitoring of a durable emission. Both methods have their respective pros and cons but operating in the intermediate time range is sometimes favorable. The pulse technique is an arrangement where the entire emission develops out during a limited amount of time usually as a flash of light in the subminute range. It is accompanied by demands for rapid mixing and initiation of the analytical process as well as fast recording techniques. Durable emission measurements are based on a slowing down of the process, e.g., by reducing the concentration of enzyme or by the addition of inhibitors, so that the light intensity may be regarded as constant during the measurements. This facilitates the measuring procedure and provides for simplified handling, but occurs at a cost of emission intensity and sensitivity. Bioluminescence analysis mimics metabolic routes yielding great possibilities for coupling with other metabolic pathways. Such coupled systems are suited for analysis of a wide variety of metabolites and enzymes. By proper kinetic design it is possible to make the analyses largely insensitive to variations in activity of the reagents.