Chemiluminescent Substrate is a reagent used in blotting techniques, particularly Western blotting, to detect specific proteins. It reacts with an enzyme—most commonly horseradish peroxidase (HRP)—that is conjugated to the antibody or probe. This enzyme–substrate reaction produces light (luminescence), which is captured using a chemiluminescence imaging system. The emitted light enables sensitive visualization and quantification of the target protein on the membrane.