LINEARIZATION OF THE BRADFORD PROTEIN ASSAY INCREASES ITS SENSITIVITY- THEORETICAL AND EXPERIMENTAL STUDIES

Determination of microgram quantities of protein in the Bradford Cooma ssie brilliant blue assay is accomplished by measurement of absorbance at 590 nm. However, an intrinsic nonlinearity compromises the sensiti vity and accuracy of this method. It is shown that under standard assa y conditions, the ratio of the absorbances, 590 nm over 450 nm, is str ictly linear with protein concentration. This simple procedure increas es the accuracy and improves the sensitivity of the assay about 10-fol d, permitting quantitation down to 50 ng of bovine serum albumin. Furt hermore, protein assay in presence of up to 35-fold weight excess of s odium dodecyl sulfate (detergent) over bovine serum albumin (protein) can be performed. A linear equation that perfectly fits the experiment al data is provided on the basis of mass action and Beer's law. (C) 19 96 Academic Press, Inc.