Minimization error for appplying amber 96 ff

GROMACS version: 5.1

Hi all,
I am using the Samson user interface (Because I am not familiar with the necessary syntax in linux) for using GROMACS for setting up the force field during the minimization step, I received the following error.

How do I circumvent this error?

Kindly help


Warning: Starting residue Gro0 (Ligand) in chain not identified as Protein/RNA/DNA.

Problem with chain definition, or missing terminal residues.

This chain does not appear to contain a recognized chain molecule.

If this is incorrect, you can edit residuetypes.dat to modify the behavior.

It says, the molecule you using in your file is not in the type of defined Protein/DNA/RNA.
You need to read gromacs manual even if you work with SAMSON

yeah, it is neither a protein nor a nucleic acid. Gro Stands for ligand in the PDB File.

pdb2gmx can’t be used for species it doesn’t know. You will have to supply parameters for any unknown species, which is usually something you do with non-GROMACS software.