Coomassie Brilliant Blue is used in which type of protein measurement approach?

• A. Dye-binding assay
• B. UV spectroscopy
• C. Immunoassay
• D. Electrochemical detection

Answer: (A)

Coomassie Brilliant Blue is used in dye-binding assays to quantify protein concentration. In the Bradford-type approach, the dye shifts from reddish to blue when it binds to proteins, and the intensity of the blue color increases with the amount of protein present. This color change is measured spectrophotometrically, typically around 595 nm, and compared to a standard curve made with known protein amounts. The method relies on the dye-protein interaction rather than the intrinsic absorbance of proteins, which is why it’s distinct from UV spectroscopy (which uses aromatic residues at 280 nm), immunoassays (which use antibodies), or electrochemical detection (which measures electrical signals).