TMB Enhanced One Component HRP Membrane Substrate is a ready-to-use solution containing 3,3′,5,5′-tetramethylbenzidine (TMB) in a mildly acidic buffer. TMB is a substrate for horseradish peroxidase. The substrate system will react with sites on the membrane containing peroxidase, producing an insoluble permanent dark blue reaction product. To stop the reaction, rinse the membrane with reagent quality water. This substrate is not recommended for microwell or immunohistochemical applications.