CALCULATE PROTEIN CONCENTRATION

Question

Calculate the protein concentration for a sample with an absorbance at 280 nm of 0.5, giving your answer in units of mg protein/ml (NOTE: ε at 280 nm = 1 cm3 mg-1 cm-1 and a cuvette of 1cm path length (l) was used in the analysis)

Answer 1

Using Beer-Lambert law:

• A = ecl where A is absorbance; e is extinction coefficient; c is concentration; l is path length
• Solving for c:  c = A/el
• c = 0.5/1 cm³mg^-1cm^-1 x 1 cm
• c = 0.5 mg/cm³ = 0.5 mg protein/ml