Loosing chain name in ".pdb" output after mdrun

GROMACS version: 2020.3
GROMACS modification: No

I am using “.pdb” as the input and output structure format for my simulation, as I needed some useful features like chain-name.

Gromacs retains the chain information in output “.pdb” structures for many of its commands, but when I run mdrun, the output structure file “.pdb” (the option -c) has lost all chain information. I checked for any options that can be used to preserve chain information, but I found none.

I needed chain information in pdb format structure file, to properly generate index groups.

Is there a way to preserve chain information?