Most sensitive chromogenic substrate for peroxidase detection, more sensitive than ABTS and OPD. It develops a deep blue color in the presence of peroxidase-labeled conjugates measurable at 650 nm. Turns yellow when stopped by acidification and read at 450 nm. Recommended for ELISA and blotting applications. 2-component format of 3, 3', 5, 5' - Tetramethylbenzidine, simply mix and use. Has longer shelf life than 1-component TMB substrates.