Electronically excited molecules in the formation and degradation of melanins.

Light emission (chemiluminescence, CL) from model reactions in vitro, relevant to the formation and degradation of melanins has been investigated. On the basis of chemiluminescence kinetics and spectra, absorption and fluorescence changes and semi-empirical calculations, it has been shown that the common exergonic step of the chemiexcitation is the oxidative opening of the six-membered ring of indoloquinone. The data indicating cytotoxic agents formation such as H2O2 O2- and 1O2 as well as the energy transfer to strong fluorescers are presented. Physiological implications of the generation of excited molecules during the biosynthesis and degradation of melanins are discussed in terms of "photobiochemistry without light."