Question

Question:Explain why the conformational freedom of peptide bonds is limited.

Short answer

The peptide bond's conformational freedom is limited due to a partial double bond character.

Step-by-step solution

Protein conformation

The condensation reaction(loss of water molecule) forms the peptide bond of protein. The protein conformation is the three-dimensional arrangement of atoms in the protein structure.

Conformational freedom of peptide bond

The peptide group has a rigid, planar structure resulting from resonance interactions that give the peptide bond approximately 40% double-bond character.The lone pairs of nitrogen are involved in resonance with the carbonyl group. It is observed that a peptide group's C-N bond is 0.13 Å shorter than its single bond and that its C=O bond is 0.02 Å longer than that of aldehydes and ketones; therefore, rotation is only possible for alpha carbon.

Hence, conformational freedom of the peptide bond is limited due to a partial double bond character in the peptide bond