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SKU AR0145
Form Solution (liquid)
Applications Western blotting, ELISA, immunofluorescence; protein expression assays, protein profiling and characterization; protein quantitation assays


Product Name Coomassie Plus Protein Assay Kit
Synonyms Coomassie Plus Bradford Assay Kit, Coomassie Plus Bradford Protein Assay Kit, Coomassie Plus Protein Quantitation Kit, Bradford Assay Protein Quantitation Kit, Bradford Assay Protein Quantification Kit
Description Coomassie Plus Protein Assay Kit is a ready-to-use, reducing agent compatible, total protein analysis reagent used for the quick determination of total protein concentration by measuring A595 and comparing to a protein standard concentration-vs.-absorption curve according to Bradford.
Application Western blotting, ELISA, immunofluorescence; protein expression assays, protein profiling and characterization; protein quantitation assays
Reagent Type Protein assay kit; Western Blotting related
Usage To be used with: Non-detergent extracted protein samples from cell lysates
Kit Components Coomassie Plus Reagent 100mL
BSA Standard 20mL(2mg/mL)

Assay information

Assay Type Protein Quantitative Measurement
Sample Type Serum, Plasma, Cell culture extracts, Other biological fluids, Tissue Extracts
Technique Solution-based detection of spectral absorbance at 595 nm; Bradford Protein assay
Detection Method Colorimetric/Spectroscopic
Equipment needed Тest tubes or miscroplates; Spectrophotometer; Microplate Reader
Assay Sensitivity 25 - 1,500 μg/ml


Form Supplied Coomassie Plus Reagent: ready-to-use 1X solution
BSA Standard: stock solution for preparing a series of standard protein dilutions
Physical State Brown-red liquid
Recommended working concentration See protocol in Datasheet
Reagent Absorbance A470 nm (brown-red)
Reagent-Protein complex Absorbance A595 nm (blue)
Activity Max activity in acidic conditions
Assays per kit Tube procedure: 50 assays
Microplate procedure: 500 assays
Compatibility with reagents Incompatible with RIPA lysis buffer and other detergent-containing lysis and extraction buffers *
Storage Store at 4˚C for one year.
Safety Phosphoric acid is a corrosive liquid

*Note: Elevated concentrations of detergent interfere with the assay. SDS interferes by either binding strongly with the protein (at low concentrations), thus inhibiting the protein binding sites for the dye reagent and causing underestimations of protein concentration in solution, or by associating strongly with the green form of the Coomassie dye, causing the equilibrium to shift towards the blue form, thus increasing the absorbance at 595 nm independent of protein presence. In this case the BCA Protein Assay Kit or Micro BCA Protein Assay Kit should be used.


The Coomassie plus protein assay k it is a quick coomassie - binding, colorimetric method for total protein quantitation based on the Bradford protein assay. When the Coomassie dye binds to protein in an acidic medium, an immediate shift in absorption maximum occurs from 465 nm to 595 nm with a concomitant color change of the solution from brown to blue. The spectrophotometric measurement of the intensity of this resulting blue color (the absorbance at 595 nm) is used to determine the concentration of protein in solutions. Protein concentrations are estimated by reference to absorbances obtained for a series of standard protein dilutions, which are assayed alongside the unknown sample.
The different colors of the coomassie dye are a result of the different charged states of the dye molecule. The blue dye molecule is an anion with an overall charge of -1. The development of color in coomassie dye-based (Bradford) protein assays has been associated with stabilizing the negatively charged state of the dye molecule by binding to certain basic / positively charged amino acids (primarily arginine, lysine and histidine) in the protein, even under acid conditions when most of the molecules in solution are in the cationic form. Van der Waals forces and hydrophobic interactions also participate in the formation of dye-protein complexes. The number of Coomassie dye ligands bound to each protein molecule is approximately proportional to the number of positive charges found on the protein. The amount of the complex present in solution is a measure for the protein concentration, and can be estimated by use of an absorbance reading. The increase of absorbance at 595 nm is proportional to the intensity of the blue of the solution, thus to the amount of bound dye, and thus to the amount (concentration) of protein present in the sample. Free amino acids, peptides and low molecular weight proteins do not produce color with coomassie dye reagents. In general, the mass of a peptide or protein must be at least 3,000 daltons to be assayed with this reagent kit.

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Coomassie Plus Protein Assay Kit
Coomassie Plus Protein Assay Kit (AR0145)
50 mL per pack, Solution (liquid)
Coomassie Plus Protein Assay Kit
Standard curve for Coomassie Plus Protein Assay Kit (AR0145)
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