Question

You are analyzing a mixture of short peptides. Part of this analysis requires you to fractionate your mixture using sulfonate (SO3-) ion-exchange chromatography. While this material works well for ion-exchange chromatography, the nature of the resin is that it ALSO very strongly interacts with hydrophobic chemical moieties, causing them to also be retained in the column. Which of the following peptides do you expect to be the first to elute from this column (at pH 7.0)?

(A) DDGPESTTP

(B) DSFIVEDVF

(C) KARILVFFRR

(D) DDSCDYKRF

(E) FFFFFDDDD

Why is the answer A?

Answer 1

# This ion exchange chromatography uses a hydrophobic ion exchanger- sulphonate ion exchanger (SO₃^-).

A hydrophobic ion exchanger strongly binds to hydrophobic molecules than hydrophilic molecules.

So hydrophilic molecules weakly binds with these kind of exchanger resines thereby, they get eluted first during elution. Here option A is mentioned as the answer which is made up of DDGPESTTP (Asp-Asp-Gly-Pro-Glu-Ser-Thr-Thr-Pro).

This peptide contains three hydroxy amino acids which are more hydrophilic in nature. So they bind weakly to the resin and get eluted faster than rest of the molecules.