Protein Concentration (Bradford) Calculator Formula
Understand the math behind the protein concentration (bradford) calculator. Each variable explained with a worked example.
Formulas Used
Protein Concentration
conc_undiluted = (absorbance - intercept) / slope * dilutionProtein Concentration
conc_mg = (absorbance - intercept) / slope * dilution / 1000Variables
| Variable | Description | Default |
|---|---|---|
absorbance | Absorbance at 595 nm | 0.45 |
slope | Calibration Slope (m) | 0.05 |
intercept | Calibration Intercept (b) | 0.02 |
dilution | Dilution Factor | 1 |
How It Works
Bradford Protein Assay
The Bradford assay uses Coomassie Brilliant Blue G-250 dye, which shifts from red to blue upon binding protein. Absorbance at 595 nm is proportional to protein concentration.
Calculation
[Protein] = (A595 - b) / m × dilution factor
where m and b come from a standard curve using BSA or another reference protein. The Bradford assay is sensitive to 1-20 ug/mL but has protein-to-protein variation.
Worked Example
A Bradford assay reads A595 = 0.45, standard curve: m = 0.05, b = 0.02, no dilution.
absorbance = 0.45slope = 0.05intercept = 0.02dilution = 1
- 01[Protein] = (0.45 - 0.02) / 0.05 × 1
- 02[Protein] = 0.43 / 0.05 = 8.60 ug/mL
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