Bicinchoninic acid is a weak acid composed of two carboxylated quinoline rings.
Bicinchoninic acid is most commonly employed by biochemists in the bicinchoninic acid assay, which is used to determine the total level of protein in a solution. In this assay, two molecules of bicinchoninic acid chelate a single Cu+ ion, forming a purple water-soluble complex that strongly absorbs light at 562 nm.