Extinction coefficient calculation
- Required for accurate protein quantification by UV absorbance
- Compare batch-to-batch concentrations
- Suitable for purified protein and antibody samples
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When the concentration of a given protein is known, the concentration and molecular weight can be used to determine the molar extinction coefficient.
It is determined using the Beer-Lambert law: A = ε ∙ L ∙ c. A is the absorbance at 280 nm, L is the light path (cm), c is protein concentration (g/L), and ε is the extinction coefficient (L g-1cm-1). When the light path L = 1cm, ε = A/c. ε value corresponds to the slope of the line plotted between absorbance and concentration.
You then calculate the extinction coefficient am (L mol-1cm-1) using the formula am = ε∙ MW, where MW is the molecular weight of the protein.
What we need from you to perform this analysis:
We will use PBS as a standard buffer system if you do not provide the buffer along with the sample.
Sample Purity
We can analyze most samples that contain proteins and peptides.
Avoid high sucrose, urea (> 2 M) or salt concentrations.
Do not use buffer that contain glycerol and high amounts of primary amines, e.g. TRIS or glycine. Because it may interfere with the ninhydrin reaction and thus provide false quantification data of specific amino acids.
Avoid fingerprints and dust in the sample. These contain large amounts of human proteins that will obscure the results.