Chemical Production of Excited States: Adventitious Biological Chemiluminescence of Carcinogenic Polycyclic Aromatic Hydrocarbons

Abstract

The chemical production of electronically excited states in biological systems falls into several categories. The first and most prominent is Bioluminescence, a late evolutionary selection for “luciferase”-catalyzed monooxygenations of “luciferin” substrates to produce light for signalling with efficiencies (photons emitted per substrate molecule reacted) close to 100% [1], Second is the delayed luminescence of pre-illuminated chloroplasts at times (10⁻⁵ sec to 10⁴ sec) too long for the process to be a primary fluorescence or slow fluorescence [2,3]. Delayed luminescence is thought to be the result of a back reaction (recombination) of photoreactants within the thylacoid that have undergone charge separation due to the primary illumination [3,4], and is, like the in vivo fluorescence of chlorophyll, non-functional. The third category which we have termed Adventitious Biological Chemiluminescence, ABC, is a non-functional, non-enzymatic light emission that occurs fortuitously and with low probability during aerobic metabolism. The literature is replete with observations, from the work of Gurwitsch beginning in the 1920’s through the present, of ABC emitted from whole tissues, from isolated cells and cell homogenates, from microsomal extracts and from purified flavoprotein oxidases and peroxidases [5–12].