Bradford Protein Assay with BSA Protein Standard

Description

Our Bradford Protein Assay is an improved, highly optimized, ready to use simple and quick colorimetric method for total protein quantitation. The assay method involves binding of the Coomassie Brilliant Blue (CBB) G-250 dye to proteins (Bradford, MM 1976). The CBB G-250 dye exists in three forms: Cationic (red), Neutral (green), and Anionic (blue) and under acidic conditions, the dye is predominantly in the doubly protonated red cationic form with A_max at 470 nm. However, when the dye binds to protein, an immediate shift in absorption maximum occurs from 470nm to 595nm with a concomitant color change from brown to blue, which can be measured using a spectrophotometer or microplate reader.

The Coomassie Brilliant Blue G-250 dye binds primarily to basic (arginine) and aromatic amino acid residues and shows constant extinction coefficient of a dye-albumin complex solution over a 10-fold concentration range. Thus, Beer Lambert’s law is very well applied for accurate quantitation of protein by selecting an appropriate ratio of dye volume to sample concentration. Performing the assay in either cuvette or microplate format is very simple, which requires combining a small amount of protein sample with the assay reagent with mixing and brief incubation, then measuring the absorbance at 595nm. The two most common protein standards used for protein assays are bovine serum albumin (BSA) and gamma-globulin. Since, dye color development in Bradford assay is significantly greater with BSA than with most other proteins, including gamma-globulin, we supply BSA standard with our kit. The supplied reagent is sufficient for 500 standard test tube assays and 2,500 standard micro-well assays.

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