How Tryptophan Oxidation Arises by “Dark” Photoreactions from Chemiexcited Triplet Acetone

Abstract

Dioxetane intermediates readily decompose to chemiluminescent triplet carbonyls, giving rise to what has been paradoxically called photochemistry in the dark. In this issue of Photochemistry and Photobiology, Bechara et al. report on mechanistic advances in such a reaction. With the use of horseradish peroxidase for isobutyraldehyde‐derived triplet acetone, light emission from acetone and singlet oxygen can be quenched. The experiments reveal that the reaction depends on oxygen and the amino acid. The analysis reveals that free tryptophan is a target of this form of “carbonyl stress,” with the efficient formation of mono‐, bi‐ and tricyclic compounds (N‐formylkynurenine, indoline, 1λ2‐indole and 3H‐indoles).