# Fatal error: Residue 225 named LYS of a molecule in the input file was mapped to an entry in the top

**URL:** https://gromacs.bioexcel.eu/t/fatal-error-residue-225-named-lys-of-a-molecule-in-the-input-file-was-mapped-to-an-entry-in-the-top/7574
**Category:** User discussions
**Created:** [November 8, 2023, 6:11am UTC](https://gromacs.bioexcel.eu/t/fatal-error-residue-225-named-lys-of-a-molecule-in-the-input-file-was-mapped-to-an-entry-in-the-top/7574 "2023-11-08T06:11:57Z")
**Posts on this page:** 1
**Page:** 1

<div class="post-metadata">

### Author: ![shivangi3800](https://avatars.discourse-cdn.com/v4/letter/s/848f3c/32.png) [@shivangi3800](https://gromacs.bioexcel.eu/u/shivangi3800)
#### Post date: [November 8, 2023, 6:11am UTC](https://gromacs.bioexcel.eu/t/fatal-error-residue-225-named-lys-of-a-molecule-in-the-input-file-was-mapped-to-an-entry-in-the-top/7574/1 "2023-11-08T06:11:57Z")

</div>

GROMACS version:  
GROMACS modification: Yes/No  
Here post your question  
hello everyone,  
i am beginner to gromacs, i have tried CHARMM and OPLS force field. but when i do pdb2gmx, it gives me this error:  
Fatal error:  
Residue 225 named LYS of a molecule in the input file was mapped  
to an entry in the topology database, but the atom CG used in  
that entry is not found in the input file. Perhaps your atom  
and/or residue naming needs to be fixed.

please tell how to fix it.  
regards  
shivangi