Bradford protein assay - Definition and Overview

The Braford protein assay is an spectroscopic analytical procedure used to measure the concentration of protein in a solution.

Principle

The Bradford Protein Assay is based on the shift of absorbance in the dye Coomassie Brilliant Blue G-250 when it is bound to arginine or aromatic amino acid residues present in the protein.

The anionic (bound) form has an absorbance spectrum maximum at 595 nm whereas the cationic (unbound) form has an absorbance maximum at 470 nm. The increase of absorbance at 595 nm is proportional to the amount of bound dye and thus, to the amount (concentration) of protein present in the sample.

Unlike other protein assays, the Bradford Protein Assay is not susceptible to interference by many chemicals that may be present in the protein sample. The exception of note is elevated concentrations of detergent.

Reference

• Bradford, M. M. (1976) A Rapid and Sensitive Method for the Quantitation of Microgram Quantities of Protein Utilizing the Principle of Protein-Dye Binding. Anal. Biochem. 72:248-254.