Peroxidase-catalyzed co-oxidation of indole-3-acetic acid and xanthene dyes in the absence of hydrogen peroxide.

The effect of xanthene dyes on the chemiluminescence from the aerobic indole-3-acetic acid (IAA) oxidation, catalyzed by horseradish peroxidase (HRP), was studied. The rate of IAA oxidation and dye destruction were controlled. It was found that the addition of dyes to the IAA/HRP/O2 system resulted in: (i) the appearance of emission in the region of dye fluorescence, (ii) an increase of the total chemiluminescence intensity, (iii) a decrease of the emission duration, (iv) the acceleration of IAA oxidation, and (v) slow bleaching of the dyes. The experimental results lead to the conclusion that all spectral and kinetic variations of the chemiluminescence from the IAA/HRP/O2 system which are caused by the addition of xanthene dyes, are the result of IAA-dye co-oxidation. Earlier published reports regarding energy transfer from electronically excited species, generated in the IAA/HRP/O2 system, to the xanthene dyes seem to be erroneous.