Charmm force field issues

User discussions
1

GROMACS version: 2022
GROMACS modification: Yes
question
Fatal error:
The residues in the chain GLN81–CYS952 do not have a consistent type. The
first residue has type ‘Protein’, while residue CSO938 is of type ‘Other’.
Either there is a mistake in your chain, or it includes nonstandard residue
names that have not yet been added to the residuetypes.dat file in the GROMACS

2

Exactly as it says, there’s a residue CSO in your protein that belongs to that chain but is not recognized as a protein residue. I assume it’s a modified amino acid?

Make a local copy of residuetypes.dat, make sure CSO is labeled as Protein, and that the corresponding .rtp entry has all the connectors that a protein residue would have to include the phi/psi dihedrals and the CMAP term:

  [ bonds ]
...
        C    +N
...
  [ impropers ]
        N    -C    CA    HN
        C    CA    +N     O
  [ cmap ]
       -C     N    CA     C    +N
3

Thank you very much for your kind reply !