mdtraj.compute_chi4

mdtraj.compute_chi4(traj, opt=True)

Calculate the chi4 torsions of a trajectory. chi4 is the fourth side chain torsion angle formed between the corresponding 4 atoms over the CD-CE or CD-NE axis (only ARG & LYS residues have these atoms)

Parameters:

traj : Trajectory

Trajectory for which you want dihedrals.

opt : bool, default=True

Use an optimized native library to calculate angles.
Returns:

indices : np.ndarray, shape=(n_chi, 4)

The indices of the atoms involved in each of the chi dihedral angles

angles : np.ndarray, shape=(n_frames, n_chi)

The value of the dihedral angle for each of the angles in each of the frames.
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