Coomassie Brilliant Blue Stain composed of s 0.25% (w/v) Coomassie Brilliant Blue G-250 in 45% (v/v) methanol and 10% (v/v) glacial acetic acid is a very common dye used for traditionally staining of protein bands in acrylamide gels after PAGE. Protein bands form an intense blue color when stained with Coomassie Brilliant Blue. This staining is very convenient as it involves a single, ready-to-use reagent and does not modify the target proteins.