ABSTRACT
Proteins bind with Coomassie Brilliant Blue G250 (CBBG,* C.I. 42655) to produce a sparingly soluble complex (1). Protein-dye binding alters the absorption spectrum for CBBG. This is the basis of the assay developed by Bradford in 1976 (2). The Bradford assay has several advantages compared with the Lowry test: (a) four-to tenfold greater sensitivity, (b) tenfold greater speed, (c) decreased susceptibility to interferences, (d) requirement for a single reagent, and (e) lower cost. The Bradford assay is quicker than dye-protein precipitation (Udy assay) as no filtration step is required. Ready-to-use CBBG dye reagent is available from Bio-Rad Laboratory Ltd., Pierce Warriner Ltd., and the Sigma-Aldrich Chemical Company. Principles of the Bradford assay are described in this chapter. Applications for food protein analysis are discussed in Chapter 7.
