The Bradford Assay
Why do protein assay? Protein assays are useful in the lab to determine protein content of cell suspensions for tissue culture purposes or for determining protein concentrations for gel electrophoresis.
The Bradford assay is one example of a protein assay and it uses a colourmetic method using a dye called Coomassie Brilliant Blue. The Coomassie dye changes colour depending on the protein concentration of a sample. Samples high in protein are bright blue, and those lower in protein are pale blue or uncoloured if the sample contains no protein at all. The assay can be used in cuvettes as part of a standard spectrophotometer assay, or can be used in 96-well microplates for a more automated rapid determination.
The Coomassie Brilliant Blue dye binds to most basic protein, but some buffers and chemicals may interfere with the assay. Therefore careful validation of any spectrophotometer assay is required.