Enter values to see results
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µg/mL
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mg/mL
Enter values to see results
—
µg/mL
—
mg/mL
The Protein Concentration (Bradford) Calculator determines protein concentration from a Bradford assay absorbance reading using the linear equation from your standard curve. The Bradford assay is one of the most widely used colorimetric methods for protein quantification, based on the binding of Coomassie Brilliant Blue G-250 dye to protein. This calculator takes your sample absorbance, standard curve parameters (slope and intercept), and dilution factor to compute the actual protein concentration.
The standard curve is a linear relationship: y = mx + b, where y is absorbance and x is concentration.
Solving for concentration:
Concentration (µg/mL) = (Absorbance − Intercept) / Slope × Dilution Factor
To use this calculator:
The Bradford assay is sensitive in the range of approximately 1–25 µg/mL (micro) or 100–1500 µg/mL (standard) depending on the protocol.
Inputs
Results
An absorbance of 0.45 with the given standard curve parameters yields a protein concentration of 66.67 µg/mL.
Inputs
Results
After accounting for a 10-fold dilution, the undiluted protein concentration is 500 µg/mL (0.5 mg/mL).
The standard Bradford assay is linear from approximately 100 to 1500 µg/mL (using the standard protocol with 1 mL reagent). The micro-Bradford variant is sensitive from 1 to 25 µg/mL. Outside these ranges, the relationship between absorbance and concentration becomes non-linear, leading to inaccurate results. Dilute concentrated samples to fall within the linear range.
Yes, SDS, Triton X-100, and other detergents commonly used in lysis buffers can interfere with Coomassie dye binding and inflate absorbance readings. Keep final detergent concentration below 0.1% SDS or 0.5% Triton X-100. If your samples contain high detergent levels, consider using a BCA (bicinchoninic acid) assay instead, which is more detergent-compatible.
The most common standard is Bovine Serum Albumin (BSA) because it is inexpensive, stable, and well-characterized. However, Bradford dye binding varies between proteins, so results are relative to the BSA standard. For absolute quantification, use a standard of the same protein you are measuring. IgG (immunoglobulin G) is another common alternative standard.
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