ABSTRACT
Hydrogen peroxide and other peroxides are directly or indirectly involved in the electronic excitation of oxidation products of many chemiluminescent and bioluminescent processes. This chapter emphasizes the in vitro and in vivo intermediacy of 1,2-dioxetane and 1,2-dioxetanone cyclic peroxides—sources of excited carbonyls by thermolysis—and consequent light emission or photochemistry. Of particular interest for their radical-like reactivity and long lifetimes are triplet carbonyls, which allow energy transfer to biomolecules or photochemistry in the absence of light and eventually trigger biological responses. Expounded upon in this chapter are mechanisms of electronic chemiexcitation in chemi- and bioluminescent processes including biomolecules catalyzed by peroxidases and accompanied by cleavage products, energy transfer to dioxygen yielding singlet oxygen, plant colchicine isomerization in the dark, phosphate-catalyzed permeation of mitochondria, initiation of lipid peroxidation of polyunsaturated fatty acids, and DNA pyrimidine dimerization in the dark.
