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Brilliant Blue (Coomassie Blue)
Known also as coomassie blue, brilliant blue is a synthetic heterocyclic organic stain, which binds nonspecifically to virtually all proteins. Although not as sensitive as silver staining, brilliant blue and its derivatives are widely utilized because of convenience.
Coomassie blue binds to proteins in an approximately stoichometric manner, meaning that when the relative amounts of protein need to be assessed, densitometry of the stained protein will provide data. Used regularly in electrophoresis, brilliant blue is sold in convenient tablets for making 0.1 percent staining solutions for the protein gels. A destaining process is often coupled to the procedure to remove excess unbound dye. Brilliant blue appears as deep blue fine crystals with a faint reddish-blue cast. Acidified coomassie blue dye changes from reddish-brown to blue when it binds to protein molecules. Other uses for brilliant blue dyes are detection of lipids in thin layer chromatography, for detection of proteins in solution and on cellulose acetate plates, and as a traceable dye for following water uptake in the roots of plants.
Brilliant blue is used as a soluble, synthetic food color in the FCF formulation. An aluminum lake color, produced by the absorption of the water-soluble brilliant blue dye onto a hydrated aluminum substrate, renders the color insoluble in water. Since lakes are pigments, their coloring abilities are achieved through dispersion of tiny color particles and not the dye purity. The more finely ground the brilliant blue color particles, the more effective the color is at a lower cost in manufacturing processes and paint production. In photography, brilliant blue has been used in toning solutions to transform black and white prints into rich, deep blue color photographs, and for creating archival prints.
To a chemist, brilliant blue is actually a diammonium salt known also as acid blue or a disodium salt, sometimes called alphazurine, featuring 37 carbon atoms, 34 hydrogens, 2 nitrogens, 2 sodiums, 9 oxygens, and 3 sulfurs per molecule. According to animal exposure trials, brilliant blue appears to be a carcinogen when injected subcutaneously, but not when ingested orally, and is banned for human use in Norway and several European countries. It also may create allergic reactions for some consumers. Certified for consumption by the United States Food and Drug Administration, brilliant blue FCF is more commonly known as Blue #1 and features an absorption maximum wavelength of 630 nanometers. Brilliant blue FCF is found in pharmaceuticals, beverages, dairy products, powders, jellies, confections, icings, syrups, extracts, and condiments. It is often combined with other dyes to arrive at the desired coloration.
Omar Alvarado, Thomas J. Fellers and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.
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