Final answer:
The angle between peptide planes is significant in determining protein structure and stability. Specifically, in secondary structures like α-helices and β-pleated sheets, and turns such as the y-turn, these angles are crucial for maintaining proper folding and function of the proteins.
Step-by-step explanation:
The angle between two peptide planes signifies the rigidity and planar nature of the peptide bonds due to their partial double bond character resulting from resonance. This fixed angle is vital to the overall three-dimensional structure of proteins, influencing their stability and function. For instance, in α-helices and β-pleated sheets, which are common secondary structures in proteins, the angles and distances between peptide planes are crucial for maintaining the integrity of these structures through hydrogen bonding and steric constraints.
In more complex turn structures like the y-turn, the angle between peptide planes helps us understand the conformation of this less common secondary structure. The y-turn involves three amino acid residues with specific geometric requirements, influencing the direction of the peptide backbone and the position of the side chain of the third residue, defining the distinction between the classic and the inverse y-turn. By studying these angles, researchers can characterise potential turn-mimicking moieties compared to experimental turn structures found in the Protein Data Bank.