Protein Extinction Coefficient

Calculate protein extinction coefficient, molecular weight, and concentration using the accurate Gill-von Hippel method

Extinction Coefficient Analysis

What is Protein Extinction Coefficient?

Protein extinction coefficient is a measure of how strongly a protein absorbs light at 280nm wavelength. It's essential for determining protein concentration from UV absorbance measurements and is calculated using the Gill-von Hippel method based on tryptophan, tyrosine, and cysteine content.

How to Use This Calculator

Calculate extinction coefficients in three simple steps:

  1. Paste your protein sequence (FASTA or plain text)
  2. Optionally enter A280 absorbance for concentration calculation
  3. View molecular weight, extinction coefficients, and concentration

When to Use

This calculator is essential for:

  • Protein purification and quantification
  • Spectrophotometric protein concentration determination
  • Bradford assay standardization
  • Protein characterization and analysis
  • Biochemical assay preparation

Example Input

Lysozyme protein sequence:

KVFGRCELAAAMKRHGLDNYRGYSLGNWVCAAKFESNFNTQATNRNTDGSTDYGILQINSRWWCNDGRTPGSRNLCNIPCSALLSSDITASVNCAKKIVSDGNGMNAWVAWRNRCKGTDVQAWIRGCRL

Try with your protein sequence or use the Example button.

Example Output

Expected results format:

Molecular Weight: 14,307 Da Molar Extinction Coefficient: 37,970 M⁻¹ cm⁻¹ Mass Extinction Coefficient: 2.653 mL mg⁻¹ cm⁻¹ Absorbance 0.1% (1 mg/mL): 2.653

Results include detailed amino acid composition and calculations.

FAQ

Q: What method is used for calculations?
A: Gill-von Hippel method with εmolar = (nW × 5500) + (nY × 1490) + (nC × 125) M⁻¹ cm⁻¹

Q: How are disulfide bonds handled?
A: Specify the number of disulfide bonds to use cystines instead of cysteines in calculations.

Q: Can I calculate protein concentration?
A: Yes, enter A280 absorbance value to get protein concentration using Beer-Lambert law.