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The φ and ψ values of a 3¹⁰-helix is composed of all D. amino acids will mainly occupy which quadrant in the Ramachandran plot?

(1) upper left

(2) upper right

(3) lower left

(4) lower right

For a typical 3¹⁰-helix composed of L-amino acids, the dihedral angles are approximately:

• φ ≈ –49°
• ψ ≈ –26°

These values place the helix in the lower left quadrant of the Ramachandran plot (where both φ and ψ are negative).

For D-amino acids, the backbone dihedral angles are the mirror images of those in L-amino acids. This means that for a 3¹⁰-helix composed of all D-amino acids, the φ and ψ values would be approximately:

• φ ≈ +49°
• ψ ≈ +26°

These positive angles place the 3¹⁰-helix in the upper right quadrant of the Ramachandran plot.

Thus, the correct answer is:

(2) upper right.