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.
restraints
dihedral
reset
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 *}
end
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.)