Question

Arrange the events employed for the determination of the primary structure of proteins.
(A). Breaking of disulfide bridges.
(B). End group analysis.
(C). Creation of overlapping fragments.
(D). Amino acid sequence determination.
Choose the correct answer from the options given below:

• A. (B), (A), (C), (D)
• B. (C), (B), (A), (D)
• C. (B), (A), (D), (C)
• D. (C), (B), (D), (A)

Hint:

Remember the logic: You must identify the chain ends first (End group analysis), separate the chains (Break disulfides), chop them into pieces (Overlapping fragments), and finally sequence those pieces (Sequence determination).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Determining the primary structure (amino acid sequence) of a protein follows a systematic chemical workflow to isolate, cleave, and analyze polypeptide chains.

Step 2: Detailed Explanation:
1. End group analysis (B): Is performed first to identify the N-terminal and C-terminal amino acids and determine the number of distinct polypeptide chains in the protein.
2. Breaking disulfide bridges (A): Polypeptide chains are separated by reducing disulfide bonds (using reagents like beta-mercaptoethanol) to yield individual linear chains.
3. Creation of overlapping fragments (C): The separated chains are cleaved at specific sites using enzymes (like trypsin) or chemical reagents (like cyanogen bromide) to generate overlapping fragments.
4. Sequence determination (D): The fragments are sequenced (e.g., via Edman degradation), and the complete sequence is reconstructed by matching overlapping regions.
5. This sequence of events yields the order: (B) \(\rightarrow\) (A) \(\rightarrow\) (C) \(\rightarrow\) (D).

Step 3: Final Answer:
The correct sequence of events is (B), (A), (C), (D).