Bradford Protein Quantification kit

The protein quantification method using Coomassie Brilliant Blue G-250 dye has been described for the first time in 1975. Three charge forms of the Coomassie Brilliant Blue dye are present in equilibrium at the usual acidic pH of the assay. The red, blue, and green forms have absorbance maxima at 470, 595, and 650 nm, respectively. The red form donates its free electron to the protein. Then the blue form interacts with the arginine, tryptophan, tyrosine, histidine and phenylalanine residues resulting in the stabilization of the blue form of the Coomassie Brilliant Blue G-250 dye. The blue anionic form is negligible at the pH of the assay reaction mixture, the binding to protein shifts the equilibrium toward its formation. The stabilized blue form of the Coomassie dye is measurable by spectrophotometry at 595 nm, the intensity of the coloration is directly linked to the amount of protein.