Coomassie Blue R-250

Coomassie Blue R-250 (CAS No.: 6104-59-2) is a synthetic anionic dye widely employed in biochemical and proteomic research as a robust protein staining reagent, particularly in sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) workflows. Functionally, it operates through non-covalent interactions, including electrostatic attraction to basic amino acid residues such as arginine and lysine and hydrophobic interactions with aromatic side chains, leading to the formation of stable dye–protein complexes that produce intense blue bands against a clear background. This mechanism underlies its utility in qualitative visualization and approximate semi-quantitative assessment of protein abundance in polyacrylamide gels, with typical detection sensitivity in the tens to low hundreds of nanograms per band. Although not associated with specific molecular targets or signaling pathways in the context of pharmacological modulation, Coomassie Blue R-250 is integral to protein analysis pipelines in drug discovery, enabling assessment of protein expression, purification efficiency, and sample integrity. The dye can exhibit metachromatic behavior, appearing red-shifted when bound to certain proteins such as collagen or histones, which may provide additional analytical insights. It is frequently used alone or in combination with more sensitive staining methods, such as silver staining, to enhance protein detection and differentiation. Experimental usage conditions vary depending on gel composition, protein load, and downstream analysis requirements, but it remains a standard reagent in in vitro assays and analytical workflows across cell biology, molecular biology, and translational research settings.