This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
Intact peptide bond is necessary for which test? 
Select and explain. 
A. UV diffraction, B. Ninhydrin, C. Diazo reaction, D. All
B: Ninhydrin
Answer: B: Ninhydrin 
Explanation: Ninhydrin, widely used for detecting amino acids, forms a purple product with -amino acids and a yellow product with the imine groups of proline and hydroxyl-proline.Ref: Harper 28th Ed. Page-20, Harper 27th Ed. Page: 20