frame_order.select_model

Select and set up the Frame Order model.

frame_order.select_model(model=None)

model: The name of the preset Frame Order model.

Prior to optimisation, the Frame Order model should be selected. These models consist of three parameter categories:

- The average domain position. This includes the parameters ave_pos_alpha, ave_pos_beta, and ave_pos_gamma. These Euler angles rotate the tensors from the arbitrary PDB frame of the moving domain to the average domain position.
- The frame order eigenframe. This includes the parameters eigen_alpha, eigen_beta, and eigen_gamma. These Euler angles define the major modes of motion. The cone central axis is defined as the z-axis. The pseudo-elliptic cone
*x*and y-axes are defined as the*x*and y-axes of the eigenframe. - The cone parameters. These are defined as the tilt-torsion angles cone_theta_x, cone_theta_y, and cone_sigma_max. The cone_theta_x and cone_theta_y parameters define the two cone opening angles of the pseudo-ellipse. The amount of domain torsion is defined as the average domain position, plus and minus cone_sigma_max. The isotropic cones are defined by setting cone_theta_x = cone_theta_y and converting the single parameter into a 2
^{nd}rank order parameter.

The list of available models are:

**`**`pseudo-ellipse`' -- The pseudo-elliptic cone model. This is the full model consisting of the parameters ave_pos_alpha, ave_pos_beta, ave_pos_gamma, eigen_alpha, eigen_beta, eigen_gamma, cone_theta_x, cone_theta_y, and cone_sigma_max.
**`**`pseudo-ellipse, torsionless`' -- The pseudo-elliptic cone with the torsion angle cone_sigma_max set to zero.
**`**`pseudo-ellipse, free rotor`' -- The pseudo-elliptic cone with no torsion angle restriction.
**`**`iso cone`' -- The isotropic cone model. The cone is defined by a single order parameter s1 which is related to the single cone opening angle cone_theta_x = cone_theta_y. Due to rotational symmetry about the cone axis, the average position
*α*Euler angle ave_pos_alpha is dropped from the model. The symmetry also collapses the eigenframe to a single z-axis defined by the parameters axis_theta and axis_phi. **`**`iso cone, torsionless`' -- The isotropic cone model with the torsion angle cone_sigma_max set to zero.
**`**`iso cone, free rotor`' -- The isotropic cone model with no torsion angle restriction.
**`**`rotor`' -- The only motion is a rotation about the cone axis restricted by the torsion angle cone_sigma_max.
**`**`rigid`' -- No domain motions.
**`**`free rotor`' -- The only motion is free rotation about the cone axis.
**`**`double rotor`' -- Restricted motions about two independent but orthogonal rotor axes. The first rotation is about the y-axis and the second is about the x-axis.

To select the isotropic cone model, type:

[numbers=none] relax> frame_order.select_model(model='iso cone')