[gmx-users] Using CHARMM force fields in Gromacs

[Jernej Zidar]

Dear all,
  I would like to do MD simulations of polymer binding to lipid bilayers.

  To that end I have generated the following components:
- CgenFF-based force field for the polymers' monomeric units (tested
in NAMD/CHARMM)
- CHARMM36 lipid force field for the lipid bilayers with some added
lipids (tested in NAMD/CHARMM)

  On the internet
(http://www.gromacs.org/Downloads/User_contributions/Force_fields) I
found the appropriate force fields (CgenFF and CHARMM36 for lipids).
How do I combine those with the monomeric residues I have generated
with ParamChem? I'm very familiar with Charmm, where all the necessary
force field can be easily combined, but I have no idea how to do it
Gromacs.

  Also worth mentioning: I will generate the initial structures of the
lipid bilayers and of the polymers in Charmm for Charmm is the only
package that can generate structures using just the internal
coordinates in the force field.

Thanks in advance for any help and tips,
Jernej Zidar