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° | RestrainDih | - | Restrain dihedral angle |
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| | | Command | | Argument | | Datatype | | Default | | Min | | Max | |
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| Format: | | RestrainDih | Atom selection 1, | |
SELECTION | | - | | - |
| - | | |
| | Atom selection 2, | | SELECTION | | - |
| - | | - | | |||
| | Atom selection 3, | | SELECTION | | - |
| - | | - | | |||
| | Atom selection 4, | | SELECTION | | - |
| - | | - | | |||
| | Class = Name of restraint class, | | STRING | | All | | - | | - | | |||
| | C = restraining energy constant in kcal/(mol*rad^2), | |
FLOAT | | 1.0 | | - |
| - | | |||
| | Equil = Equilibrium angle in degrees, | | FLOAT | | - | | - | | - | | |||
| | Delta = allowed plus/minus range in degrees, | | FLOAT | | - | | - | | - | | |||
| | Exponent = restraining energy exponent | | FLOAT | | 2.0 | | - | | - | | |||
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| Python: | | RestrainDih(selection1,selection2,selection3,selection4,Class,c,equil,delta,exponent=None) | | ||||||||||
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| Menu: | | Simulation > Restrain > Dihedral |
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| Related: | | RestrainDis, LoadTbl , RestrainPot, RestrainPar , RestEnergy, RestViol , ScaleRest, ListRest , ShowRest, HideRest , DelRest | | ||||||||||
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| Required: | |  and the NMR Structure Determination Module |
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The
RestrainDih command adds a dihedral angle restraint to the four selected atoms,
that forces this dihedral to fall into the range Equil+/-Delta during a
simulation or internal coordinate folding run
.
The restraining function is the same as used by XPLOR:
 | (1) |
and
| (2) |
where Phi is the current dihedral angle, the scaling factor Scale
can be modified afterwards with the ScaleRest
command, while the individual scaling factor C, the equilibrium dihedral angle
Equil, the allowed deviation Delta, and the Exponent are set directly by this command or
read from a restraint file in XPLOR format
. For clarity, the fact that differences between dihedral angles must consider the wrap-around at
+/-180 degrees has been omitted from equation 2.
The restraints can be
shown or hidden
on screen and deleted. They are not part of the scene and therefore not affected by undo/redo and not saved with
SaveSce. Restraints are deleted automatically when the object they belong to is modified.
Satisfied restraints are drawn green, violated ones red. They can be styled using the
PointPar command and the JoinDis option of the
RestrainPar command.
Example:
RestrainDih C Res 10,N Res 11,CA Res 11,C Res 11,C=2.0,Equil=-50,Delta=20
Restrain the backbone dihedral angle 'Phi' of residue 11 to
-50+/-20 degrees with an energy constant of 2 kcal/(mol*rad^2).