Photometric Estimation of Protein Content in Biological Suspensions

Abstract

The quantitation of protein in suspensions of biomembranes and cells is one of the most topical problems in biological research. Colorimetric methods based on a chemical reaction between a reagent and protein are extensively applied [126, 127]. The most widely used methods are the biuret reaction and the Lowry assay [127, 128]. Unfortunately, many of the compounds used in enzyme purification interfere with the reaction. To overcome this problem, modifications are required [127]. Furthermore, the accuracy of these methods depends on the number of Trp and Tyr residues in a protein. Other methods are based on the change in the absorbance of certain dyes, which bind to proteins [129–131]. In these methods the resulting color depends, to a limited extent, on the composition of the protein, therefore, accurate protein quantification requires a calibration using an appropriate protein mixture [127].