Ramachandran plot - validate the torsion angles of a protein chain.

Thus, only torsion angles (φ, ψ) are allowed to vary between -180 and 180 .

First, the decoys are generated by perturbing pairs of torsion angles by an amount δ.

During each cycle, we begin from the native conformation and energy minimize the conformations with respect to the torsion angles.

The plastic grips well and makes bonds difficult to rotate, so that arbitrary torsion angles can be set and retain their value.

In calmodulin, torsion angles change for five residues in the middle of a domain linking α-helix.

Under this fixed angle, the segments are still free to rotate and all torsion angles are equally likely.

The hindered rotation model assumes that the torsion angle is hindered by a potential energy.

This makes the probability of each torsion angle proportional to a Boltzmann factor:

The spatial arrangement described by the torsion angles of the molecule is known as its conformation.