The Bio-Rad protein assay is a simple colorimetric assay for measuring total protein concentration and is based on the Bradford dye-binding method (Bradford 1976). Immunoglogin G (IgG - gamma globulin) is the preferred protein standard.

Protein Quantification in the Presence of Poly(ethylene Glycol) and Dextran Using the Bradford Method Anal Biochem . The Bradford assay is is the fastest and easiest to perform among the protein assays and uses about the same amount of protein as the Lowry assay. The name 'Bradford protein assay' comes from the first person to develop it, Marion M. Bradford. The Bradford protein assay was developed by Marion M. Bradford in 1976. When the Bradford reagent (acidified Coomassie Brilliant Blue G-250) binds to proteins, the dye undergoes a color change in the visible spectrum, with the absorbance maximum moving from 470 to … How the Bradford Protein Assay Works. Using standard procedure, the assay is used with samples having protein concentrations between 200 and 1,400 µg/ml (20–140 µg total). Bradford protein assay. It is a quick and accurate spectroscopic analytical procedure used to measure the concentration of protein in a solution. The Bradford assay, a colorimetric protein assay, is based on an absorbance shift of the dye Coomassie Brilliant Blue G-250.The Coomassie Brilliant Blue G-250 dye exists in three forms: anionic (blue), neutral (green), and cationic (red). This method is fairly new, as it was developed within the last 50 years. The reaction is dependent on the amino acid composition of the measured proteins. The Bradford assay is rather sensitive to bovine serum albumin, more so than "average" proteins, by about a factor of two. The assay requires the preparation of a working solution from supplied reagents. 2009 Dec 1;395(1):108-10. doi: 10.1016/j.ab.2009.07.045. The assay development requires long incubations of 30 minutes up to 2 hours. The Bradford protein assay is a time-tested colorimetric assay.

Under acidic conditions, the red form of the dye is converted into its blue form, binding to the protein being assayed.