Protein Concentration Calculator
Find protein concentration from an A280 reading.
Estimate protein concentration via UV absorbance (Beer–Lambert law).
How the Math Works
The Protein Concentration Calculator uses the formula conc = A280 ÷ (ε × path) to determine protein concentration from absorbance data. A280 measures how much light a protein sample absorbs at 280 nm, while ε (extinction coefficient) represents how strongly the protein absorbs light at this wavelength, specific to each protein type. The 'path' variable refers to the light path length through the sample, typically 1 cm for standard cuvettes. This equation is derived from the Beer-Lambert Law, which relates absorbance to concentration, and allows users to calculate concentration by accounting for the protein's unique absorption properties and measurement conditions.
Practical Applications
To use this calculator practically, first measure the A280 absorbance of your protein sample using a spectrophotometer. You'll need the extinction coefficient (ε) for your specific protein—if unknown, look it up in scientific literature or use a standard curve with known concentrations. Ensure the cuvette path length (path) is entered correctly, usually 1 cm. Input these values into the formula: divide the absorbance reading by the product of ε and path length. For example, if A280 is 0.8, ε is 1.4 (for BSA), and path is 1 cm, the concentration is 0.8 ÷ (1.4 × 1) = 0.57 mg/mL. Always verify ε values for accuracy, as incorrect coefficients significantly affect results.
Day-to-Day Use
This calculation is essential in laboratories worldwide for daily tasks like preparing protein solutions, validating sample purity, or ensuring consistent concentrations in experiments. Researchers rely on accurate protein measurements for techniques such as Western blotting, enzyme assays, or cell culture, where incorrect concentrations can invalidate results. In biotechnology or food science, it helps verify protein content in products or optimize manufacturing processes. By quickly estimating concentration from simple absorbance readings, scientists save time compared to labor-intensive methods like chromatography, making it a cornerstone of efficient and reliable research workflows.
Worked example
A280 0.8, 1 cm, ε 1 → 0.8 mg/mL.
FAQ
Exact ε?
Calculate it from the protein's amino-acid sequence for accuracy.