Question

Let's say that an unknown protein has an isoelectric point of 7.0.

a) Will this protein be positively or negatively charged at pH 4.0?

b) Will this protein be an anion or a cation at pH 10.0?

c) If you had at your disposal a cation exchange column, would you separate the protein from others in the mix on the basis of cation exchange or anion exchange? Explain. d) Would phosphate buffer (pKa 7.20), ethanolamine buffer (pKa 9.50), or citric acid buffer (pKa 3.13) be best suited for the cation exchanger for this protein? Explain why in terms of the predominant charge state of this protein under a buffered pH range.

Answer 1