b'Chromogenic western blot detectiondevelop as well. Where chromogenic substrates fail in terms of sensitivity, they are ideal for applications where Chromogenic or precipitating substrates have been usedprotein abundance is high. Because the product of the widely for many years and offer the simplest and mostenzymesubstrate reaction is a colored precipitate, the cost-effective method of detection. When these substratessignal is stable, and therefore chromogenic substrates come in contact with the appropriate enzyme, they aredo not typically have issues with false-negative results converted to insoluble, colored products that precipitate(ghost bands) that can occur with chemiluminescent onto the membrane (Figure 34). The resulting colored bandsubstrates. An added advantage of chromogenic detection or spot requires no special equipment for processing oris that the reaction can be stopped when the desired visualizing. Chromogenic blotting substrates are availablesignal has been achieved, which minimizes saturation of in a variety of specifications and formats. The appropriatesignal. However, unlike with chemiluminescent blotting substrate choice depends on the enzyme label andassays, the colored precipitate cannot be easily stripped desired sensitivity.off for reprobing. The performance of a particular substrate may vary dramatically when obtained from different The low sensitivity of chromogenic substrates makessuppliers. This is because performance can be affected it difficult to detect proteins of low abundance. Thoughby the concentration and purity of the substrate and by the reaction can be allowed to develop for several hoursother additives and buffer components that are a part of or even overnight, this also allows background signal tothe formulation.Figure 34. Overview of an enzymesubstrate reaction during chromogenic western blot detection.54'