This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
At physiological pH, carboxy terminal of peptide is 
Select and explain. 
A. Positive charged, B. Negative charged, C. Neutral, D. Infinitely charged
B: Negative charged
Answer: B: Negative charged 
Explanation: 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