Question

Match List - I with List - II.

List - I	List - II
A. Biuret reactions	I. \(\alpha\)-Amino acid
B. Ninhydrin test	II. Two peptide linkage
C. Millon's reaction	III. Guanidino group
D. Sakaguchi reaction	IV. Phenolic group (Tyr)

Choose the correct answer from the options given below:

• A. A-II, B-I, C-IV, D-III \
• B. A-I, B-II, C-III, D-IV \
• C. A-IV, B-III, C-II, D-I \
• D. A-II, B-III, C-IV, D-I

Hint:

Ninhydrin is the classic general test for all $\alpha$-amino acids, while the Biuret test requires a minimum of two peptide bonds to react.

Answer 1

The Correct Option is A

Step 1: Concept Qualitative chemical tests for proteins are designed to spot specific functional groups inside amino acid side chains or along the underlying peptide backbone matrix.

Step 2: Meaning * General protein assays recognize shared structural attributes like the peptide backbone or the amino group. * Specific assays detect unique chemical arrangements on individual amino acid side chains.

Step 3: Analysis * Biuret reactions (A) detect the presence of at least two peptide linkages where copper ions form a purple coordination complex in alkaline conditions $\rightarrow$ (A-II). * Ninhydrin test (B) is a general test for any free $\alpha$-amino acid, reacting with the primary amino group to yield a deep purple-blue pigment called Ruhemann's purple $\rightarrow$ (B-I). * Millon's reaction (C) identifies the phenolic group unique to Tyrosine side chains through nitrification and complexation with mercury ions $\rightarrow$ (C-IV). * Sakaguchi reaction (D) specifically identifies the guanidino functional group found on Arginine side chains using $\alpha$-naphthol and sodium hypobromite $\rightarrow$ (D-III).

Step 4: Conclusion The resulting configuration reads A-II, B-I, C-IV, D-III, which matches option A. Final Answer: (A)