# Group Protein\_UNK referenced in the .mdp file was not found in the index file

**URL:** <https://gromacs.bioexcel.eu/t/group-protein-unk-referenced-in-the-mdp-file-was-not-found-in-the-index-file/6468>\
**Category:** User discussions\
**Tags:** mdp-parameters\
**Created:** [May 22, 2023, 6:03pm UTC](https://gromacs.bioexcel.eu/t/group-protein-unk-referenced-in-the-mdp-file-was-not-found-in-the-index-file/6468 "2023-05-22T18:03:05Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Tanvir](https://avatars.discourse-cdn.com/v4/letter/t/e99b99/32.png) [@Tanvir](https://gromacs.bioexcel.eu/u/Tanvir)\
**Post date:** [May 22, 2023, 6:03pm UTC](https://gromacs.bioexcel.eu/t/group-protein-unk-referenced-in-the-mdp-file-was-not-found-in-the-index-file/6468/1 "2023-05-22T18:03:05Z")

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GROMACS version:21  
Fatal error:  
Group Protein\_UNK referenced in the .mdp file was not found in the index file.  
Group names must match either [moleculetype] names or custom index group  
names, in which case you must supply an index file to the ‘-n’ option  
of grompp.

As the error suggest Protein\_UNK is not found in the index file. But surely i have generated Protein\_UNK . Anyone please help to solve this error .  
 ![npt_error](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/b/b0af2d466c023e6261691927d919e5d08439f2db.jpeg)

**index file**  
 ![index_error](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/3/3a87bec9610650b799b721e823815a7172994c87.jpeg)

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**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\
**Post date:** [May 22, 2023, 6:28pm UTC](https://gromacs.bioexcel.eu/t/group-protein-unk-referenced-in-the-mdp-file-was-not-found-in-the-index-file/6468/2 "2023-05-22T18:28:15Z")

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The existence of an index file is insufficient; did you do this:

> [@Tanvir](#):
>
> in which case you must supply an index file to the ‘-n’ option  
> of grompp.

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**Author:** ![Tanvir](https://avatars.discourse-cdn.com/v4/letter/t/e99b99/32.png) [@Tanvir](https://gromacs.bioexcel.eu/u/Tanvir)\
**Post date:** [May 22, 2023, 6:43pm UTC](https://gromacs.bioexcel.eu/t/group-protein-unk-referenced-in-the-mdp-file-was-not-found-in-the-index-file/6468/3 "2023-05-22T18:43:08Z")

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Thanks . Now it works just fine … Thanks a lot again .