[gmx-users] What is best way to get multiple chains?

[ms]

Hi,

I am a gmx newbie, so please don't bite too much! :)

Learning gmx, I am experimenting with simulations with multiple
identical small chains. What I did was:

- I generated the peptides with pymol
- Generated a .gro with pdb2gmx
- Used editconf to create translated copies
- Stitching them together and creating the complete file, adjusting
numbers etc. manually

It worked well, but the chains are not recognized as *different* chains
-which could be useful. Documentation says I should use another format
like the pdb, but it is a bit sparse on the subject. I think I can use
pdb instead of gro if needed, but does this also work when creating
boxes etc.? Isn't there a way to get chain identifiers in a gro file?
What is best practice?

Thanks a lot,
Massimo