Final answer:
The rotation of the polypeptide backbone (folding conformation) is limited by steric hindrance, torsional angles, and electrostatic repulsion.
Step-by-step explanation:
The rotation of the polypeptide backbone (folding conformation) is limited due to steric hindrance, torsional angles, and electrostatic repulsion.
Steric hindrance occurs when bulky or large side chains come too close to each other, preventing free rotation of the polypeptide backbone.
Torsional angles, also known as dihedral angles, define the allowed orientations of the peptide bonds, restricting the possible conformations of the backbone.
Electrostatic repulsion between like charges on the peptide backbone can also limit the rotation of the polypeptide backbone.