<prompt> At physiological pH, carboxy terminal of peptide isPositive chargedNegative chargedNeutralInfinitely charged  <response>: 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 