Coomassie Brilliant Blue R-250 is one of the most common forms of coomassie dye, which is a key component of various colorimetric protein gel stains. Coomassie Brillant Blue R-250 staining solution is the fastest and easiest way to stain proteins on precast gels or other polyacrylamide protein gels.
Coomassie R-250 and G-250 dyes are two chemical forms of a disulfonated triphenylmethane compound that is commonly used as the basis of stains for detection of proteins in gel electrophoresis and Bradford-type assay reagents for protein quantitation. The R-250 (red-tinted) form lacks two methyl groups that are present in the G-250 (green-tinted) form, which is also called colloidal coomassie dye. Typically, coomassie gel stains and protein assay reagents are formulated as very acidic solutions in 25 to 50% methanol. In acidic conditions, the dye binds to proteins primarily through basic amino acids (primarily arginine, lysine and histidine), and the number of coomassie dye ligands bound to each protein molecule is approximately proportional to the number of positive charges found on the protein. Protein-binding causes the dye to change from reddish-brown to bright blue (absorption maximum equals 595 nm).
• Easy detection—Develops intensely colored complexes with proteins
• High sensitivity—Can determine as little as 0.5 µg/cm2 of protein present in a gel matrix
• Reversible staining—Anion of Coomassie Brilliant Blue formed in the acidic staining medium combines with the protonated amino groups of proteins by electrostatic interaction; resulting complex is reversible under the proper conditions
• Differentiation between bound and unbound dye—When dissolved in 0.01M citrate buffer at pH 3.0, has an absorption maximum at 555nm; protein-dye complex is characterized by a peak slightly broader than that of the free dye with a maximum at 549 nm
1 L, 1 Gal