14. The position of collagen triple helix in Ramachandran plot is at-
    (1) Top Left
    (2) Top right
    (3) Bottom right
    (4) Bottom left

Collagen Triple Helix Position in the Ramachandran Plot

The Ramachandran plot is a crucial tool in structural biology that illustrates the allowed dihedral angles (ϕ, Ψ) of amino acids in proteins. Different secondary structures, such as α-helices, β-sheets, and collagen triple helices, occupy distinct regions on this plot.

Correct Answer:

The collagen triple helix is found in the top left region of the Ramachandran plot.

Explanation of the Answer Choices

1. Collagen Triple Helix Position (Correct Answer: Top Left)

• The collagen triple helix consists of three polypeptide chains wound around each other.
• Each chain adopts a left-handed polyproline type-II helix with dihedral angles:
  • ϕ ≈ -60°
  • Ψ ≈ 150°
• These angles place collagen in the top left quadrant of the Ramachandran plot.

2. Why Are Other Options Incorrect?

• Top Right (Incorrect): This region corresponds to rarely observed conformations, not common secondary structures.
• Bottom Right (Incorrect): This region is generally disallowed due to steric clashes.
• Bottom Left (Incorrect): This region is occupied by right-handed α-helices, not the left-handed collagen helix.

Significance of Collagen Triple Helix

1. Structural Role in Connective Tissue

• Collagen is a key component of skin, tendons, and cartilage.
• Its triple-helical structure provides mechanical strength and stability.

2. Importance in Protein Folding

• The stability of collagen depends on its hydroxylation and glycine content.
• Mutations in collagen genes lead to disorders like osteogenesis imperfecta.

3. Applications in Biotechnology

• Collagen-based biomaterials are used in tissue engineering and regenerative medicine.
• Understanding its structure aids in designing synthetic peptides for medical applications.

Conclusion

The collagen triple helix occupies the top left region of the Ramachandran plot, corresponding to its left-handed polyproline II helical structure. This unique positioning is essential for its biological function, mechanical properties, and role in connective tissue stability.