To seperate biochemglobin protein pI 68 from bioglobin throu

To seperate biochemglobin protein (pI= 6.8) from bioglobin through ion exchange chromatography with CM-cellulose resin particles, the MOST OPTIMAL pH of the buffer should be:

a. =6.8

b. >6.8

c. <6.8

d. pI does not make a difference in this case

e. pH does not make a difference in this case

Solution

CM-cellulose resin particles has a carboxymethyl functional group -CH2OCH2COOH. At neutral pH the carboxymethyl group is ionized as -CH2OCH2COO¯ so that CMcellulose is negatively charged, so it is a weak cation exchanger

In a buffer with a pH lower than the pI of the protein of interest, the protein will carry a positive net charge; thus a negatively-charged cation exchange resin is chosen.

Here the protien of interest is biochemglobin which as a pl = 6.8 , CM-cellulose resin particles are cation exchangers and hence buffer should have a pH< pl of biochemglobin i.e (<6.8) and hence choice c is the correct answer