Free Beer-Lambert Protein Calculator
Calculate protein concentration from UV absorbance at 280 nm using the Beer-Lambert law and known extinction coefficient.
Mass Concentration
0.0010 mg/mL
Mass Concentration vs Absorbance at 280 nm
Protein Concentration from A280
UV absorbance at 280 nm is widely used to measure protein concentration. Aromatic residues (Trp, Tyr) and disulfide bonds absorb at this wavelength.
Formula
c (M) = A280 / (epsilon × l)
c (mg/mL) = c (M) × MW / 1000
The extinction coefficient epsilon can be calculated from the amino acid sequence using tools like ProtParam. Typical values range from 10,000 to 100,000 M⁻¹cm⁻¹.
Example Calculation
A protein with epsilon = 43,000 M⁻¹cm⁻¹ and MW = 45 kDa, measured A280 = 1.0 in a 1 cm cuvette.
- 01c = 1.0 / (43000 × 1) = 2.326 × 10⁻⁵ M = 23.26 uM
- 02c = 23.26 × 10⁻⁶ × 45000 / 1000 = 1.047 mg/mL
Frequently Asked Questions
Learn More
Understanding Molarity
Learn what molarity is, how to calculate it, and why it matters in chemistry. Covers moles, liters, dilution, and step-by-step examples for preparing solutions.