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The method combines the reactions of copper ions with the peptide bonds under alkaline conditions (the Biuret test) with the oxidation of aromatic protein residues. The Lowry method is based on the reaction of Cu +, produced by the oxidation of peptide bonds, with Folin–Ciocalteu reagent (a mixture of phosphotungstic acid and phosphomolybdic acid in the Folin–Ciocalteu reaction).
Several reliable methods for quantifying protein have been developed to simplify the process. These methods include Warburg–Christian method, Lowry assay, and Bradford assay (all of which rely on absorbance properties of macromolecules). Bradford assay method uses a dye to bind to protein. Most commonly, Coomassie brilliant blue G-250 dye is ...
Additionally, the BCA protein assay gives the important benefit of compatibility with substances such as up to 5% surfactants in protein samples. In the Lowry protein assay, Cu + is oxidized back to Cu 2+ by Mo VI in the Folin–Ciocalteu reagent, which forms molybdenum blue (Mo IV).
As of September 2015, his 1951 paper in the Journal of Biological Chemistry [5] describing the protein assay was still the most-highly cited paper in history, with more than 310,000 citations, [6] although Lowry stated it was not the most important paper he had ever written.
The most cited paper of all time [12] [13] [14] was published in the journal by Oliver H. Lowry on Protein measurement with the Folin phenol reagent [15] and describes the Lowry protein assay, and has been cited well-over 300,000 times. [12]
BCA protein assay in a 96 well plate. The bicinchoninic acid assay (BCA assay), also known as the Smith assay, after its inventor, Paul K. Smith at the Pierce Chemical Company, [1] now part of Thermo Fisher Scientific, is a biochemical assay for determining the total concentration of protein in a solution (0.5 μg/mL to 1.5 mg/mL), similar to Lowry protein assay, Bradford protein assay or ...
The BCA protein assay method maintains the high sensitivity and low variability among proteins associated with the Lowry protein assay, while providing increased tolerance to the presence of non-ionic detergents and buffer salts. The BCA assay has since become one of the most widely used methods of protein quantitation.
The Lowry method is sensitive to protein concentrations as low as 20 ug/mL. The disadvantage of this method is the long incubation time and there are often interferences with commonly used buffers. This method is also subject to protein-to-protein variation due to the correlation of colour intensity dependent on the content of tyrosine and ...