Coomassie® Blue G250, C.I. 42655, is a triphenylmethane dye used for protein staining in SDS-PAGE and for colorimetric protein quantification. It is also known as Coomassie Brilliant Blue G-250, Brilliant Blue G-250, and Acid Blue 90.
Synonyms: Coomassie Brilliant Blue G-250; Brilliant Blue G-250; Acid Blue 90.
In Bradford-type assays, protein binding stabilizes the blue form of Coomassie Brilliant Blue G-250, producing an absorbance response measured at 595 nm. Dye response varies with protein composition and sample matrix, so quantitative measurements should be performed against an appropriate protein calibration curve.
For Cat. 03707, λmax is 610 nm. Bradford assays are read at 595 nm after protein binding; these wavelengths reflect different measurement conditions and should not be used interchangeably.
Key Properties
- Triphenylmethane dye used for protein staining and dye-binding assays
- Color Index Number: C.I. 42655
- CAS Number: 6104-58-1
- Molecular weight: 854.03 g/mol
- Appearance: deep-blue crystals with a reddish tint
- λmax: 610 nm
- Bradford assay measurement wavelength: 595 nm
- Catalog number: 03707
- Storage: room temperature
Applications
SDS-PAGE Protein Staining
Coomassie® Blue G250 is used to visualize proteins separated by SDS-polyacrylamide gel electrophoresis. Band intensity and background depend on protein load, gel composition, stain formulation, staining time, and destaining conditions.
Bradford-Type Protein Quantification
Coomassie Brilliant Blue G-250 is the dye used in Bradford-type protein assays. Protein binding shifts the dye population toward the blue form, which is quantified spectrophotometrically at 595 nm. Protein concentration is determined by comparison with a calibration curve prepared from an appropriate protein standard.
Protein Assay Development
G250 is also used in method-development studies examining protein-dependent dye response, calibration behavior, buffer compatibility, and interference from detergents or other sample components.
Compatibility & Bonding Considerations
- Bradford response varies among proteins because dye binding depends on protein composition and accessible binding sites
- Quantitative assays should use standards prepared in a matrix that closely matches the unknown samples
- Buffer composition, detergents, and other sample components can influence background absorbance and dye response
- The 610 nm λmax of Cat. 03707 is distinct from the 595 nm wavelength used to quantify the protein-bound dye in Bradford assays
- Coomassie Blue G250 and Coomassie® Blue R250 are chemically distinct dyes and should be selected according to the staining or analytical method
Protein staining intensity and quantitative dye response depend on dye formulation, protein composition, concentration, sample matrix, incubation conditions, and measurement protocol.
Application Tips
- Prepare protein standards in the same or closely matched buffer system used for the unknown samples
- Include an appropriate reagent blank and calibration curve for quantitative Bradford measurements
- Maintain consistent reagent volumes, incubation time, and measurement timing across standards and samples
- Evaluate detergent compatibility when analyzing protein samples containing surfactants
- For gel staining, maintain consistent staining and destaining conditions when comparing band intensity across samples or gels
Handling & Storage
- Store at room temperature in a cool, well-ventilated location
- Keep the container closed when not in use
- Minimize generation and inhalation of dye dust
- Use with good laboratory ventilation
- Wear protective gloves, safety glasses, and suitable protective clothing during handling
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FAQ
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1. What is Coomassie Blue G250 used for?
Coomassie® Blue G250 is used for staining proteins in SDS-polyacrylamide gels and for dye-binding protein quantification, including Bradford-type assays.
2. Are Coomassie Blue G250, Brilliant Blue G-250, and Acid Blue 90 the same dye?
Yes. Coomassie Brilliant Blue G-250, Brilliant Blue G-250, and Acid Blue 90 are names used for C.I. 42655, CAS Number 6104-58-1.
3. Why are both 610 nm and 595 nm associated with Coomassie Blue G250?
Cat. 03707 has an absorbance maximum at 610 nm under its dye-characterization conditions. In Bradford-type protein assays, binding to protein changes the spectral response of G250, and the resulting protein-dye complex is quantified at 595 nm.
4. Is Coomassie Blue G250 the same as Coomassie Blue R250?
No. Coomassie® Blue G250 is C.I. 42655, CAS Number 6104-58-1. Coomassie® Blue R250 is C.I. 42660, CAS Number 6104-59-2. They are distinct dyes and should be used according to the applicable staining or assay protocol.
5. What should be considered when using G250 for quantitative protein assays?
Use an appropriate protein standard, matched buffer conditions, a reagent blank, and consistent assay timing. Protein-dependent dye response and interference from sample components such as detergents can affect quantitative results.
Safety & Documentation
Coomassie® Blue G250 can irritate the skin and eyes and may be harmful if inhaled. Use good laboratory ventilation and appropriate personal protective equipment. Refer to the product Safety Data Sheet (SDS) for complete handling, storage, first-aid, and disposal guidance.
