# Dihedral restraints

**URL:** <https://ask.bioexcel.eu/t/dihedral-restraints/131>\
**Category:** HADDOCK\
**Created:** [June 13, 2016, 3:53am UTC](https://ask.bioexcel.eu/t/dihedral-restraints/131 "2016-06-13T03:53:40Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![acook](https://avatars.discourse-cdn.com/v4/letter/a/ecb155/32.png) [@acook](https://ask.bioexcel.eu/u/acook)\
**Post date:** [June 13, 2016, 3:53am UTC](https://ask.bioexcel.eu/t/dihedral-restraints/131/1 "2016-06-13T03:53:40Z")

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Hi all,

I’m trying to submit some dihedral restraints for the protein backbone in my Haddock runs. Does anyone know what the file format for this is? I know there’s a link on the website, but it doesn’t seem to work for me.

Cheers!

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**Author:** ![mtrellet](https://dub1.discourse-cdn.com/flex013/user_avatar/ask.bioexcel.eu/mtrellet/32/42_2.png) [@mtrellet](https://ask.bioexcel.eu/u/mtrellet)\
**Post date:** [June 13, 2016, 6:52am UTC](https://ask.bioexcel.eu/t/dihedral-restraints/131/2 "2016-06-13T06:52:03Z")

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Hello,

The file format we’re using is TBL and the restraints must look like the following line:

`assign (resid 1 and name c ) (resid 2 and name n ) (resid 2 and name ca) (resid 2 and name c ) 1.0 -125.0 25.0 2`

where the generic pattern follows:

`assign <atom selection> < atom selection> <atom selection> <atom selection> <force constant> <target dihedral angle> <error range> <exponent>`

You can find the information in this paper: [http://www.nature.com/nprot/journal/v5/n5/full/nprot.2010.32.html](http://www.nature.com/nprot/journal/v5/n5/full/nprot.2010.32.html)

I hope this will help!