# Distance restraints between more than one protein and ligand

**URL:** <https://gromacs.bioexcel.eu/t/distance-restraints-between-more-than-one-protein-and-ligand/5382>\
**Category:** User discussions\
**Created:** [December 7, 2022, 9:39am UTC](https://gromacs.bioexcel.eu/t/distance-restraints-between-more-than-one-protein-and-ligand/5382 "2022-12-07T09:39:45Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![sallaprat](https://avatars.discourse-cdn.com/v4/letter/s/f08c70/32.png) [@sallaprat](https://gromacs.bioexcel.eu/u/sallaprat)\
**Post date:** [December 7, 2022, 9:39am UTC](https://gromacs.bioexcel.eu/t/distance-restraints-between-more-than-one-protein-and-ligand/5382/1 "2022-12-07T09:39:45Z")

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GROMACS version: 2021  
GROMACS modification: No

Dear all,

I am simulating a dimeric protein that binds ATP+Mg2+. I would like to use distance restraints for each ATP and Mg2+ molecules and each protein monomer. I cannot set [bonds] between them because they are different topology files.

I have read that you can set distance restraints with the pull code. Is it possible to use the pull code for 4 distance restraints? I have only managed to use the pull code for one distance and I am struggling to make it work for more than one.

Thank you very much in advance,

Sara

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**Author:** ![hess](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/hess/32/416_2.png) [@hess](https://gromacs.bioexcel.eu/u/hess)\
**Post date:** [December 7, 2022, 2:55pm UTC](https://gromacs.bioexcel.eu/t/distance-restraints-between-more-than-one-protein-and-ligand/5382/2 "2022-12-07T14:55:25Z")

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You can add harmonic or flat-bottomed potentials in the [intermolecular\_interactions] section.