Bradford Assay Calculator

The Bradford assay is a colorimetric method used in labs to measure protein concentration in a sample. Enter your sample absorbance at 595 nm, standard curve slope, intercept, and dilution factor into the Bradford Assay Calculator to get the protein concentration in mg/mL. Secondary outputs include concentration in µg/mL and optional molar concentration (µM) if you provide the protein's molecular weight.

AU

Measured absorbance of your sample at 595 nm

Slope from your protein standard curve (y = mx + b)

Y-intercept from your protein standard curve

Factor by which your sample was diluted (1 = no dilution)

Da

Optional: For molar concentration calculations

Results

Protein Concentration

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Concentration (µg/mL)

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Molar Concentration

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Frequently Asked Questions

What are the main advantages of using Bradford assay for protein quantification?

The Bradford assay is fast, simple, and compatible with many reducing agents and salt solutions. It provides good sensitivity with a detection range of 1-1400 µg/mL and uses an inexpensive, stable dye reagent.

How does the Bradford assay work at a molecular level?

The assay is based on the binding of Coomassie Brilliant Blue G-250 dye to proteins. When the dye binds to proteins, it shifts from its cationic (red) form to its anionic (blue) form, causing an increase in absorbance at 595 nm.

What are the units for my protein concentration results?

Bradford assay results are typically expressed in mg/mL or µg/mL. With molecular weight information, concentrations can also be calculated in molar units (µM or mM) for specific applications.

How do I generate protein standards for the standard curve?

Use a known protein like BSA (bovine serum albumin) to create standards ranging from 0-2000 µg/mL. Plot absorbance vs concentration to generate the linear equation (y = mx + b) needed for calculations.

Can Bradford assay be used with all types of proteins?

Bradford assay works with most proteins but may show variability with different protein types due to varying numbers of basic amino acid residues. It's less accurate for proteins rich in acidic residues or lacking basic amino acids.

What are common pitfalls to avoid when performing Bradford assay?

Avoid using detergents like SDS which interfere with the assay, ensure consistent incubation times, use fresh reagents, and account for any sample dilutions in your final calculations.

How does Bradford assay compare to other protein quantification methods?

Bradford is faster than Lowry but less sensitive than BCA assay. It's more tolerant of reducing agents than Lowry but less compatible with detergents than BCA. A280 is faster but requires pure proteins.

Why do I need to apply dilution factors in my calculations?

If your sample was diluted before the assay, you must multiply the calculated concentration by the dilution factor to get the true concentration of your original sample. This accounts for the sample preparation steps.