This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Proteins and Amino Acids, Subject name: Biochemistry
An amino acid that does not form an a-helix is: 
Select and explain. 
A. Asparagine, B. Tyrosine, C. Tryptophan, D. Proline
D: Proline
Answer: D: Proline 
Explanation: Ans. D. ProlineProline which is also called an imino acid always destabilizes a-helix. Other amino acids which disrupt the helix are acidic and basic.