[gmx-users] POPC membrane simulations

[Chris Neale]

If I understand correctly you want to construct popc.itp from the 
dppc.itp that is available on Tieleman's site? And you have used PRODRG 
to do this? That sounds like a lot of extra work when popc.itp is 
directly available from Tieleman's site...
http://moose.bio.ucalgary.ca/index.php?page=Structures_and_Topologies

The fact that you want to use ffG53a5 and not ffgmx is more of an issue. 
To do that you need to avoid lipid.itp and do something like this:
http://www.gromacs.org/pipermail/gmx-users/2006-September/023639.html
However, you will want to heed this warning (or at least understand it):
http://www.gromacs.org/pipermail/gmx-users/2006-September/023640.html

Chris.