The Amplite® Colorimetric Bradford Protein Quantitation Assay Kit is a colorimetric assay that quantifies protein concentration by measuring the absorbance shift of Coomassie Brilliant Blue G-250 dye from brown to blue. In acidic conditions, the dye exists in a reddish-brown cationic form (maximum absorbance at 470 nm). Upon binding to proteins, it forms strong, noncovalent complexes and shifts to a blue anionic form with a peak absorbance at 595 nm. The increase in absorbance at 595 nm is directly proportional to the protein concentration in solution. Unlike UV-based 280 nm measurements that rely on aromatic amino acids, the Bradford method is based on interactions with basic amino acids such as arginine, lysine, and histidine. This allows for visible-spectrum detection and even visual inspection of protein content. While the traditional linear range is limited to ~10 µg/mL due to spectral overlap, using a dual-wavelength ratio (595/460 nm) significantly extends the assay’s dynamic range, improving accuracy at higher protein concentrations.