In: Chemistry
You have a mixture of proteins with the following properties, using a cation exchange column, what would be the order of elution for the following mixture of proteins
MW pHI
A. 85,000 7.0
B. 65,000 6.2
C. 35,000 9.5
Cation exchange columns are the reverse, negatively charged beads which attract positively charged proteins. If the functional group is negatively charged (e.g. a carboxylate group), they bind positively charged molecules (cation exchange).
pH < 7 will have a net positive charge due to protonation, pH = 7 being neutral zwitterionic type(isoelectric point pl), whereas pH > 7 will have a net negative charge.
Hence the order of elution will be
C. 35,000 9.5 -------> A. 85,000 7.0 ----> B. 65,000 6.2
↑
↑
↑
First eluted --------> second
elution -----> last elution
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