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The Bradford protein assay is a spectroscopic analytical procedure used to measure the concentration of protein in a solution.
Principle
The Bradford assay, a colorimetric protein assay, is based on an absorbance shift in the dye Coomassie when bound to arginine and hydrophobic amino acid residues present in protein.
The anionic (bound) form of the dye has an absorption 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 less susceptible to interference by various chemicals that may be present in protein samples. An exception of note is elevated concentrations of detergent.
Alternative assays
Alternative protein assays include
- UV spectroscopy
- Biuret protein assay
- Lowry protein assay
- Bicinchoninic acid protein assay
- Amido black protein assay
- o-phthalaldehyde protein assay
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.
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