– The Bicinchoninic acid (BCA) assay is a stable, sensitive and highly compatible method for the determination of protein concentration. It is commonly used for quantifying the total amount of proteins after extraction. The detection mechanism of BCA assay involves two reations. The first reation is based on the biruet reaction, in which the protein chelates with copper (II) ion in an alkaline environment and reduces the copper (II) to copper (I), forming a blue complex. The second reaction is the chelation of BCA with the cuprous ion, resulting in an intense purple color. The purple colored reaction product is formed by the chelation of two molecules of BCA with one cuprous ion. The complex exhibits a strong linear absorbance at 562 nm with increasing protein concentrations.