Protein Extinction Coefficient Calculator
Calculate protein extinction coefficient from amino acid composition
About this calculator
The Protein Extinction Coefficient Calculator determines the molar extinction coefficient of proteins based on their amino acid composition. This essential tool helps researchers calculate protein concentrations using Beer-Lambert law by analyzing the contribution of aromatic amino acids (tryptophan, tyrosine, and cysteine) that absorb UV light at 280nm. Accurate extinction coefficients are crucial for protein quantification, purification protocols, and biochemical assays in molecular biology and protein research.
How to use
Enter your protein's amino acid sequence or specify the number of tryptophan, tyrosine, and cysteine residues in the designated fields. The calculator will automatically compute the extinction coefficient at 280nm based on established absorption values for each aromatic amino acid. Use the result to determine protein concentration using spectrophotometric measurements.
Frequently asked questions
What wavelength does this calculator use for extinction coefficient?
The calculator determines extinction coefficient at 280nm wavelength, which is standard for protein UV absorption measurements in spectrophotometry.
Which amino acids contribute to protein extinction coefficient?
Tryptophan, tyrosine, and cysteine (disulfide bonds) are the primary contributors to protein extinction coefficient due to their aromatic properties.
How accurate is the calculated extinction coefficient?
The calculation is highly accurate for most proteins, typically within 5-10% of experimental values when using standard amino acid absorption coefficients.