The horseradish peroxidase-catalyzed oxidation of 3, 5, 3', 5'-tetramethylbenzidine. Free radical and charge-transfer complex intermediates.

PD Josephy, T Eling, RP Mason - Journal of Biological Chemistry, 1982 - ASBMB
Benzidine and related compounds are well known substrates for horseradish
peroxidase/H2O2 oxidation. Typically, two different colored products are formed. In this
paper, we study the oxidation of 3, 5, 3', 5'-tetramethylbenzidine. The first colored product is
a blue charge-transfer complex of the parent diamine and the diimine oxidation product. This
species exists in rapid equilibrium with the radical cation. The radical was observed by ESR
spectroscopy, and hyperfine splitting constants were determined. Addition of equimolar …