Photo chemi luminescence of tryptophan containing peptides and proteins on photo oxidation part 2 ketone sensitized photo chemi luminescence of glycyl tryptophan solutions Sapezhinskii, I.I.; Dontsova, Y.G. Biophysics (English Translation of Biofizika) 18(6): (1974) 1973 https://eurekamag.com/research/027/143/027143296.php