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': 'Which one of the following is not true for an α-helix \nSelect and explain. \nA. It is one of the most important secondary structure, B. It has a net dipole moment, C. All hydrogen bonds are aligned in the same direction, D. Long stretches of left handed α-helices occur in proteins', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Right-handed (clockwise) α-helix is more stable and therefore is the usual α-helix pattern found in the natural secondary structure. Left-handed α-helix is not common.\nα-helix is the most common secondary structure in proteins.\nα-helix has an overall dipole moment: amino terminus of an alpha helix is positive and carboxy terminus is negative.\nAll hydrogen bonds in a-helix are parallel (i.e. in the same direction).', 'role': 'assistant'}]