At physiological pH, carboxy terminal of peptide is: (A) Positive charged, (B) Negative charged, (C) Neutral, (D) Infinitely charged
Answer is B. In ion-exchange chromatography, proteins interact with the stationary phase by charge-charge interactions. Proteins with a net positive charge at a given pH will tightly adhere to beads with negatively charged functional groups such as carboxylates or sulfates (cation exchangers).
 
Harper, Ed 30, Pg 27