In a Ramachandran diagram the region representing the angles of $\phi$ and $\varPsi$ that correspond to those commonly made by an amino acid that favors a left-handed $\alpha$ helix are different from those angles commonly made by an amino acid that favors right-handed $\alpha$ helix formation.Which of the following statements provides a plausible explanation for this difference?
A)Groups which would normally undergo high steric hindrance in the right-handed arrangement are separated maximally in the left-handed arrangement.
B)Left-handed helices have smaller pitch than right-handed helices.
C)The peptide backbone can coil tighter in the left-handed helices than in the right-handed helices.
D)Left-handed helices exhibit cyclic symmetry,while righthanded helices are asymmetric.
E)All of the above are plausible explanations.

Question

Quizplus · Accepted Answer

The steric hindrance between groups in the peptide backbone is reduced in the left-handed helix conformation, allowing for more optimal bonding angles and resulting in a higher likelihood for left-handed helix formation by residues that favor this conformation. This is not specifically addressed by the other answer choices.

In a Ramachandran Diagram the Region Representing the Angles Of \phi