# How to add Position restrain in .mdp file

**URL:** <https://gromacs.bioexcel.eu/t/how-to-add-position-restrain-in-mdp-file/7320>\
**Category:** User discussions\
**Tags:** mdp-parameters\
**Created:** [October 3, 2023, 6:21am UTC](https://gromacs.bioexcel.eu/t/how-to-add-position-restrain-in-mdp-file/7320 "2023-10-03T06:21:06Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Sahil](https://avatars.discourse-cdn.com/v4/letter/s/f6c823/32.png) [@Sahil](https://gromacs.bioexcel.eu/u/Sahil)\
**Post date:** [October 3, 2023, 6:21am UTC](https://gromacs.bioexcel.eu/t/how-to-add-position-restrain-in-mdp-file/7320/1 "2023-10-03T06:21:06Z")

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I have created the topology file using AMBERTools and converted the topology file for Gromacs. Now, I want to equilibrate the molecule, which is a protein-DNA complex. Is there any way I can modify the .mdp file to select the particular atoms or residues for **position restrain**?