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Dihedral Angle Restraints

    The following example shows how to set up torsion angle restraints. Coupling constant measurements provide a means to obtain information about certain dihedral angles, albeit with low precision. The low precision makes it necessary to employ rather large error ranges.



    assign (resid 1 and name c) (resid 2 and name ca)
      (resid 2 and name n) (resid 2 and name c)  1 -120.0 40.0 2   {* 9 Hz *}
    assign (resid 2 and name c) (resid 3 and name ca)
      (resid 3 and name n) (resid 3 and name c)  1 -120.0 50.0 2   {* 8 Hz *}

The four selections of each assign statement specify the particular dihedral angle. The first number after the selections specifies the energy constant (C) in kcal mole rad, the second number specifies degrees to which the dihedral angle is restrained (), the third number specifies the range around the restrained angle (), and the last number specifies the exponent of the restraining function. (Refer to Section 7.2 for more information.)

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