Extinction Coefficient
Extinction Coefficient — A measure of how strongly a substance absorbs light at a given wavelength, used to determine peptide concentration via UV spectrophotometry.
What Is the Extinction Coefficient?
The molar extinction coefficient (ε, M⁻¹cm⁻¹) quantifies how strongly a peptide absorbs light at a specific wavelength, enabling concentration determination via the Beer-Lambert law (A = εcl). For peptides, ε280 is calculated from Trp (5,500), Tyr (1,490), and Cys-Cys (125) contributions.
Calculation
- Formula: ε280 = (nTrp × 5,500) + (nTyr × 1,490) + (nCys-Cys × 125)
- No Trp/Tyr: Peptides without aromatic residues have negligible A280. Use A214 (peptide bond) instead
- Tools: ExPASy ProtParam calculates ε from sequence
Frequently Asked Questions
What is Extinction Coefficient?
A measure of how strongly a substance absorbs light at a given wavelength, used to determine peptide concentration via UV spectrophotometry.
Why is Extinction Coefficient important in peptide research?
Extinction Coefficient is a fundamental concept in analytical as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.
Authority Sources
- Extinction Coefficient on Wikipedia
- Search Extinction Coefficient on PubChem (NIH)
- Research articles on ScienceDirect