The Thermo Scientific Pierce BCA Protein Assay Kit is a two-component, high-precision, detergent-compatible assay reagent set to measure (A562nm) total protein concentration compared to a protein standard.

Used in more labs than any other detergent-compatible protein assay, Pierce BCA Reagents provide accurate determination of protein concentration with most sample types encountered in protein research. The Pierce BCA Assay can be used to assess yields in whole cell lysates and affinity-column fractions, as well as to monitor protein contamination in industrial applications. Compared to most dye-binding methods, the BCA Assay is affected much less by protein compositional differences, providing greater protein-to-protein uniformity.

Colorimetric– estimate visually or measure with a standard spectrophotometer or plate reader (562nm)

Excellent uniformity– exhibits less protein-to-protein variation than dye-binding methods

Compatible– unaffected by typical concentrations of most ionic and nonionic detergents

Moderately fast– much easier and four times faster than the classical Lowry method

High linearity– linear working range for BSA equals 20 to 2000µg/mL

Sensitive– detect down to 5µg/mL with the enhanced protocol

Studying protein:protein interactions

Measuring column fractions after affinity chromatography

Estimating percent recovery of membrane proteins from cell extracts

High-throughput screening of fusion proteins

Time comparison of BCA Protein Assay Reagent vs. Lowry Protein Assay.
BCA Protein Assay Reagent 1. Mix reagents 1 minute 2. Add sample and incubate 30 minutes 3. Read at 562nm 1 minute Total BCA Time: 32 minutes	Lowry Protein Assay 1. Make reagents 70 minutes 2. Add sample and incubate 20 minutes 3. Add Folin Reagent 1 minute 4. Incubate 30 minutes 5. Read at 750nm 1 minute Total Lowry Time: 122 minutes

Standard curves.Typical standard curves for bovine serum albumin (BSA) and bovine gamma globulin (BGG) in the BCA Protein Assay. Kits include ampules of Albumin Standard.

The BCA Protein Assay combines the well-known reduction of Cu²⁺to Cu¹⁺by protein in an alkaline medium with the highly sensitive and selective colorimetric detection of the cuprous cation (Cu¹⁺) by bicinchoninic acid. The first step is the chelation of copper with protein in an alkaline environment to form. a light blue complex. In this reaction, known as the biuret reaction, peptides containing three or more amino acid residues form. a colored chelate complex with cupric ions in an alkaline environment containing sodium potassium tartrate.

In the second step of the color development reaction, bicinchoninic acid (BCA) reacts with the reduced (cuprous) cation that was formed in step one. The intense purple-colored reaction product results from the chelation of two molecules of BCA with one cuprous ion. The BCA/copper complex is water-soluble and exhibits a strong linear absorbance at 562 nm with increasing protein concentrations. The BCA reagent is approximately 100 times more sensitive (lower limit of detection) than the pale blue color of the first reaction.

The reaction that leads to BCA color formation is strongly influenced by four amino acid residues (cysteine or cystine, tyrosine, and tryptophan) in the amino acid sequence of the protein. However, unlike the Coomassie dye-binding methods, the universal peptide backbone also contributes to color formation, helping to minimize variability caused by protein compositional differences.

For more information, see the article "Chemistry of Protein Assays" in the Protein Methods Library.

1.       Smith, P.K., et al. (1985). Anal. Biochem. 150: 76-85.

2.       Sorensen, K. (1992). BioTechniques 12(2): 235-236.

3.       Ju, T., et. al. (2002). J. Biol. Chem. 277: 178-186.

4.       Shibuya, T., et. al. (1989). Tokyo Ika Daigaku Zasshi 47(4): 677-682.

5.       Hinson, D.L. and Webber, R.J. (1988). BioTechniques 6(1): 14-19.

6.       Akins, R.E. and Tuan, R.S. (1992). BioTechniques 12(4): 496-499.

7.       , ;, ;, ;Tylianakis, P.E., et. al.(1994). Anal. Biochem. 219(2): 335-340.

8.       Gates, R.E. (1991). Anal. Biochem. 196(2): 290-295.

9.       Stich, T.M. (1990). Anal. Biochem. 191: 343-346.

10.    Tuszynski, G.P. and Murphy, A. (1990). Anal. Biochem. 184(1): 189-191.