Protein Concentration Calculator

Category: Biology
- March 11, 2025
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Typical values range from 0.5 to 2.0
Standard cuvettes have a 1 cm path length
If sample was diluted before measurement (e.g., 5 = 1:5 dilution)

The concentration of protein using absorbance at 280 nm (A280) is determined using the Beer-Lambert Law:

\[ C = \frac{A}{\epsilon \times l} \]

where:

  • \( C \) = Protein concentration (mg/mL)
  • \( A \) = Absorbance at 280 nm
  • \( \epsilon \) = Extinction coefficient (L·g⁻¹·cm⁻¹)
  • \( l \) = Path length of the cuvette (cm)

What is the Protein Concentration Calculator?

The Protein Concentration Calculator helps determine protein concentration using different methods, including:

  • Absorbance at 280 nm (A280): A quick and non-destructive method based on aromatic amino acids.
  • Bradford Assay: A colorimetric method using dye binding.
  • BCA (Bicinchoninic Acid) Assay: A method relying on copper reduction and colorimetric detection.
  • Lowry Assay: A well-established approach using protein-copper interactions.

How to Use the Calculator

Follow these steps to calculate protein concentration:

  • Select the measurement method (A280, Bradford, BCA, or Lowry).
  • Enter the required values such as absorbance, dilution factor, and extinction coefficient (if needed).
  • If using a standard curve method (Bradford, BCA, or Lowry), input the curve parameters.
  • Click the "Calculate" button to get the concentration result.

Benefits of Using the Calculator

  • Saves time by automating concentration calculations.
  • Supports multiple measurement methods for flexibility.
  • Includes a dilution calculator for preparing specific concentrations.
  • Reduces human error in manual calculations.

FAQs

1. How accurate is the Absorbance (A280) method?

The A280 method is generally accurate for pure proteins but can be affected by contaminants like nucleic acids.

2. Can I use the Bradford Assay for all proteins?

The Bradford Assay works well for most proteins but may give variable results depending on the protein composition.

3. What is the advantage of the BCA Assay?

The BCA method is more compatible with detergents and has a broader linear range than Bradford.

4. How do I choose the correct extinction coefficient for A280?

Use published values for known proteins, or calculate the extinction coefficient based on amino acid composition.

5. Why do I need a dilution factor?

If your sample is diluted before measurement, you must multiply the calculated concentration by the dilution factor to obtain the correct final concentration.