Luminescence in Clinical Analysis

Many chemiluminescent reactions are used for analytical purposes. The main reason is the high sensitivity that is obtained with relatively simple instruments. In biology and medicine, the most widely used luminescence assays are based on enzyme-catalysed bioluminescent reactions. These have the additional advantage of being highly speci­ fic, of having high quantum yield, and of being adaptable for analysis of many biologically relevant substances. Bioluminescent reactions have been observed in a great number of organisms belonging to essentially all major phyla. Most systems consist of an enzyme, luciferase, catalysing the oxidation by 02 or H202 of a substrate, luciferin, the reaction ultimately re­ sulting in light emission. The colour of the emitted light varies with the species from blue to red, depending on the type of luciferinjluciferase system involved. The present discussion will be restricted to the firefly and bacterialluciferase reactions, the stoichio­ metries of which are summarised in the formulae below: firefly Iuciferase ATP + luciferin + 02 -~AMP +PP M g 2+