[63] Visible-range low-level chemiluminescence in biological systems

Abstract

This chapter discusses the application of visible-range low-level chemiluminescence in biological systems. Two photoemissive processes, fluorescence and phosphorescence, can follow excitation and are collectively termed low-level chemiluminescence or bioluminescence. Singlet oxygen and triplet carbonyls are likely to account for most of the chemiluminescence in biological systems, but it should be mentioned that the formation and emission from excited species probably represent only minor side reactions of the biological pathways that act as their source. Highly sensitive photodetectors can measure the low-level (or ultraweak) chemiluminescence accompanying these processes even in complex biological systems. The monitoring of this low-level chemiluminescence has been used together with other methods of assessing oxidative processes within cells, but it has the advantages of being noninvasive and providing continuous monitoring. In addition to the procedures for the direct measurement of ongoing chemiluminescence, the specific enhancers and quenchers of activated compounds can aid in the identification of the luminescent species in some biological systems.