What is the Difference Between Bradford and Lowry Protein Assay?

The Bradford and Lowry protein assays are both colorimetric techniques used to determine protein concentrations in solutions. However, they have some key differences:

1. Principle: The Bradford assay is based on the absorbance shift of the dye Coomassie brilliant blue G-250, while the Lowry assay involves the interaction of protein with an alkaline copper tartrate solution and Folin-Ciocalteu reagent.
2. Amino acid composition dependence: The Bradford assay is dependent on the amino acid composition of the protein, particularly arginine, lysine, and histidine, while the Lowry assay is not.
3. Time: The Bradford assay takes about 15 minutes to produce a result, while the Lowry assay takes 40-60 minutes.
4. Sensitivity: The Bradford assay is more accurate at lower protein concentrations than the Lowry assay.
5. pH and buffer types: The Bradford assay is sensitive to the pH of buffers and types of detergents used, while the Lowry assay is not.

In summary, the Bradford assay is quicker and more accurate at lower protein concentrations, but it is dependent on the amino acid composition and sensitive to pH and buffer types. The Lowry assay is less affected by these factors but takes longer to produce results.

Comparative Table: Bradford vs Lowry Protein Assay

Here is a table comparing the Bradford and Lowry protein assays:

Both the Bradford and Lowry assays are colorimetric techniques used to determine protein concentration in a solution. The Bradford assay relies on the absorbance shift of the dye Coomassie brilliant blue G-250, while the Lowry assay uses copper ions and the Folin–Ciocalteu reagent. The Bradford assay is faster and less susceptible to interference from other compounds, but it is less consistent than the Lowry assay.