[gmx-users] how to keep chain ID?

[Albert]

hello:

I've got a large protein contains five chains. I assigned the FF with 
PDB2GMX and it split them into different .itp file. after running 
minimization, I found that the em.gro contains no chain informations. I use

editconf -f em.gro -o em.pdb

to convert it into .pdb file and it doesn't have chain ID either.

I am wondering, how can I keep chain ID informations?

thank you very much
best
Albert