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
[{'content': 'Amino acid with dissociation constant closest to physiological pH is: \nSelect and explain. \nA. Serine, B. Histidine, C. Threonine, D. Proline', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Histidine has dissociaion constant close to physiologic pH of 7.4 Ref: Textbook of Biochemistry By DM Vasudevan, 3rd Edition, Page 15 ; Lippincott Biochemistry, 2nd Edition, Pages 9-10 ; Pulmonary Biology in Health and Disease By E. Edward Bittar, 2002, Page 277', 'role': 'assistant'}]