BCA Protein Assay kit (BCA-PAK) is useful for colorimetric detection and quantification of total protein content, even in the presence of detergents.

BCA-PAK is based on the reduction of Cu²⁺ to Cu¹⁺ by protein in alkaline solution; monovalent copper ions produced are detected in a concentration dependent manner. Bicinchoninic acid (BCA) chelates with the reduced copper Cu¹⁺ and forms a water-soluble purple reaction complex that exhibits a strong absorbance at 562 nm. Absorbance is linear over a wide range of protein concentrations between 25 to 2000 µg/ml. In general, protein concentrations are estimated with reference to a commonly used protein standard; the kit also includes Bovine Serum Albumin (BSA) at 1,5 mg/ml as a protein standard for a convenient preparation of protein concentration standard curves.