Question

Calculate the concentration of protein in your purified AP fraction using the literature extinction coefficient for AP at 280 nm.

Given: the absorbance of AP at 280nm was 0.240 abs.

Answer 1

Ans. Beer-Lambert’s Law, A = e C L                     - equation 1,              

where,

                                                A = Absorbance

                                                e = molar extinction coefficient (M^-1cm^-1)

                                                L = path length (in cm)

                                                C = Molar concentration

Extinction coefficient of alkaline phosphate (AP) = 31390 M^-1 cm^-1 at 280 nm

[Ref: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2622731/

# Putting the values in equation 1-

            0.240 = (31390 M^-1 cm^-1) x C x 1.0 cm

            Or, C = 0.240 / (31390 M^-1) = 7.645 x 10^-6 M

Therefore, [Protein] in given sample = 7.645 x 10^-6 M