Bicinchoninic Acid Assay

Bicinchoninic Acid Assay designates a colorimetric protein quantification method based on biuret reaction where peptide bonds reduce cupric ions to cuprous ions in alkaline solution, which then form a purple complex with two bicinchoninic acid molecules detectable spectrophotometrically at 562 nanometres, providing sensitive protein concentration measurement.

The biopharmaceutical industry employs the bicinchoninic acid assay widely for protein quantification during manufacturing, purification monitoring, and quality control. Its compatibility with detergents, reducing agents, and many common buffer components makes it versatile for diverse sample types encountered in downstream processing. However, certain compounds including strong reducing agents at high concentrations interfere, requiring sample dilution or alternative methods. The assay is commonly used alongside other quantification methods providing complementary information. Automated microplate formats enable high-throughput sample analysis supporting process development studies requiring numerous concentration measurements across multiple process conditions and timepoints.