Protein Concentration Calculator (A280)
Calculate protein concentration from absorbance at 280 nm using Beer-Lambert law with the protein's extinction coefficient.
How to Use the Protein Concentration Calculator
- Measure the absorbance of your protein sample at 280 nm.
- Enter the A280 value.
- Enter the dilution factor applied to the sample.
- Enter the extinction coefficient for your protein (mL·mg⁻¹·cm⁻¹).
- Click Calculate to get the protein concentration.
使用场景
- •Quantifying purified recombinant proteins after chromatography.
- •Determining antibody concentration for therapeutic formulation.
- •Monitoring protein recovery across purification steps.
公式
Formula: concentration (mg/mL) = A280 × dilution factor / extinction coefficient (mL·mg⁻¹·cm⁻¹).
常见问题
What extinction coefficient should I use?
The molar extinction coefficient is protein-specific and depends on Tryptophan, Tyrosine, and Cysteine content. For IgG antibodies, a common value is 1.4 mL·mg⁻¹·cm⁻¹. Use ExPASy ProtParam to calculate it from the amino acid sequence.
When is A280 measurement preferred over Bradford/BCA?
A280 is non-destructive, fast, and does not consume sample. However, nucleic acid contamination (A260) and other UV-absorbing compounds can interfere.
Disclaimer
For educational and laboratory purposes only. Accuracy depends on using the correct extinction coefficient for the specific protein and ensuring the sample cuvette path length is 1 cm.