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: Physiology
[{'content': 'Replacing alanine by which amino acid will increase UV absorbance of protein at 280nm wavelength: \nSelect and explain. \nA. Leucine, B. Proline, C. Arginine, D. Tryptophan', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Tryptophan', 'role': 'assistant'}]