Application of an eosin B dye method for estimating a wide range of proteins

We describe a detailed procedure for estimating a wide range of proteins by the eosin B dye method. At acidic pH, eosin B binds to proteins and absorption of the protein-dye complex at 536-544 nm is proportional to the concentration of the proteins. Inorganic and organic acids are used for the assay, the optimum concentration of acid for each assay differs from acid to acid. This method provides minimal interference with commonly used compounds in protein purification and biomolecules like DNA, RNA, lipids, carbohydrates and minerals which are generally present in biological fluids. This method is applicable for estimating proteins in tissue homogenates, isolated proteins and various biological fluids.