[gmx-users] converting pdb of protein+ATP+water+ion into gromacs files

[Dina Mirijanian]

Hello,
I am trying to convert a protein+ATP+water+ion system pdb into gromacs
files.  I need to use the existing water and ion coordinates.  I can
convert the protein part using pdb2gmx and grompp fine.  But, I do not know
how to process the solvent and ion coordinates separately and combine them
to make the final system.  Can anyone give me direction?  I am new to
gromacs...
Thanks you very much.
-Dina