Bradford protein assay
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This article is about a scientific procedure. See Bradford (disambiguation) for other entries about Bradford.
The Bradford Protein Assay is a spectroscopic analytical procedure used to measure the concentration of protein in a solution.
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[edit] 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 is blue and has an absorption spectrum maximum historically held to be at 595 nm. The cationic (unbound) forms are green and red. 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.
[edit] Disadvantages
The Bradford assay is linear over a short range, typically from 2ug/ml to 120ug/ml, often making dilutions of a tissue sample necessary before analysis.
[edit] 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
[edit] 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.
