Issue with covalent protein-ligand model/Adding ions step

GROMACS version: gmx grompp, version 2023-openSUSE
GROMACS modification: Yes/No
Hi all,

I am working on my covalent ligand-protein model (Cys-ligand) and adding Cys-ligand as a new residue to FF (charmm36-jul2022.ff). I got an issue using

gmx grompp -f ions.mdp -c solv.gro -p topol.top -o ions.tpr

Generated 167799 of the 167910 non-bonded parameter combinations

Generating 1-4 interactions: fudge = 1

Generated 117432 of the 167910 1-4 parameter combinations

ERROR 1 [file topol.top, line 950]:

Atomtype ns not found


Program: gmx grompp, version 2023-openSUSE

Source file: src/gromacs/gmxpreprocess/toppush.cpp (line 1436)

Fatal error:

There was 1 error in input file(s)

For more information and tips for troubleshooting, please check the GROMACS

website at Common Errors — GROMACS webpage https://www.gromacs.org documentation

Line 950 in topol.top file is corresponding to N atom of Cys that makes peptide bond with neighboring ASN residue in protein. I have used for acpype for parametrization of Cys-lig model and modified aminoacids.rtp, aminoacids.hdb and aminoacids.rtp files accordingly.

I appreciate any help/suggestion fixing issue.

Bests

Zahra