[gmx-users] Re: gmx-users Digest, Vol 14, Issue 31

jaime arce at ibsm.cnrs-mrs.fr
Fri Jun 10 10:37:42 CEST 2005

> Hi All,
> I am having a bit of trouble with the a membrane simulation. I am using the ffG45a3 forcefield from the contributions page but after 5ns the lipid surface area approaches 57 A^2, which is below what it should be. Has anyone used this forcefield? Below is my .mdp file and the top file for the a DPPC lipid, the origonal bilayer was from peter tielemans site (dppc64.pdb). 
> If anyone has any suggestions...
> Many Thanks
> John 

Hi john, 
I am also using the ffG45a3 forcefield and I would like to know more
about your problem. Does the lipid surface area is really signicantly
different from experimental data (experimental errors included) ?
If so, and if you think the membrane is well relaxed the problem is
either the forcefield or your topology. I agree that you should try the
newer ffG53a5, but this forcefield is quite similar to ffG45a3 and I'll
be surprised if the results obtained were fundamentally different from
what you previously obtained. If this is the case you should perhaps
change the topology, especially if this was optimized for other
forcefiels such as ffgmx.

jaime <arce at ibsm.cnrs-mrs.fr>

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