Question

The \(\alpha\)-helical structure of proteins are the result of formation of hydrogen bonds between which of the following amino acids in its primary structure?

• A. nth and n + 4th
• B. nth and n + 2nd
• C. nth and n + 3rd
• D. nth and n + 5th

Hint:

\(\alpha\)-helix:
- H-bond between n and n+4.
- 3.6 amino acids per turn.
- Stabilized by intra-chain hydrogen bonds.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
This question tests knowledge of protein secondary structure.

Step 2: Detailed Explanation:
In an \(\alpha\)-helix, hydrogen bonds form between the carbonyl oxygen of the nth amino acid and the amide hydrogen of the (n+4)th amino acid.
This pattern stabilizes the helical structure.
The \(\alpha\)-helix has 3.6 amino acids per turn.
(n+2) and (n+3) are not the correct spacing for \(\alpha\)-helix formation.
(n+5) is also not correct.
Thus, the correct spacing is nth and n+4th.

Step 3: Final Answer:
Thus, hydrogen bonds form between nth and n+4th amino acids, which corresponds to option (A).
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