# One control to constrain a molecule type

**URL:** <https://gromacs.bioexcel.eu/t/one-control-to-constrain-a-molecule-type/12834>\
**Category:** User discussions\
**Created:** [October 27, 2025, 12:05am UTC](https://gromacs.bioexcel.eu/t/one-control-to-constrain-a-molecule-type/12834 "2025-10-27T00:05:16Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![rmdughmi](https://avatars.discourse-cdn.com/v4/letter/r/e56c9b/32.png) [@rmdughmi](https://gromacs.bioexcel.eu/u/rmdughmi)\
**Post date:** [October 27, 2025, 12:05am UTC](https://gromacs.bioexcel.eu/t/one-control-to-constrain-a-molecule-type/12834/1 "2025-10-27T00:05:16Z")

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GROMACS version:2023  
GROMACS modification: No

Dear all,

I was wondering if there’s a control to put inside the .mdp so i put constraint on whole molcule\_type so they dont deform or change shape while maintaining their translational and rotational motion.

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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:** [November 11, 2025, 11:40am UTC](https://gromacs.bioexcel.eu/t/one-control-to-constrain-a-molecule-type/12834/2 "2025-11-11T11:40:12Z")

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No, GROMACS has no such option.