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During the purification of a mixture of proteins listed in the table below: Whic

ID: 70521 • Letter: D

Question

During the purification of a mixture of proteins listed in the table below: Which protein binds most tightly to a CM-cellulose column running at pH 7.5? Which protein will run through a gel filtration column first? Which one will come out last? Which proteins are unlikely to be resolved by gel filtration chromatography? Which protein will be eluted last from a DEAE-cellulose column at pH 7.5? Protein G runs on a SDS-PAGE gel as two bands of molecular masses 40 and 60 kD. How many polypeptide chains make up this protein? Propose a two-step purification strategy for protein C.

Explanation / Answer

a. At neutral pH, CM cellulose is negatively charged and binds more positively charged proteins. Therefore, it binds protein (F).

b. Protein G with highest molecular wt. will run through a gel filtration column first. Protein B with lowest mol. wt will come last.

c. At neutral pH, DEAE cellulose is positively charged and binds more negatively charged proteins. Therefore, it binds protein (E).