[gmx-users] membrane simulation

[Anirban Ghosh]

On Thu, May 3, 2012 at 4:38 PM, <scaprari at uniroma3.it> wrote:

> Hi all,
> I'm new in Membrane simulations with Gromacs. I have to simulate a system
> made up of a protein just leant on a membrane patch which has previously
> been extended and made it free of periodicity (with trjconv). I'm reading
> the "KALP15 in DPPCI" Tutorial and, so far, I managed to obtain my protein
> (in pdb code) very close to the membrane surface by using editconf and cat
> command. At this point, I don't know how to get on. 1)How should I
> generate the topology file which includes  the coordinates both of the
> protein and of the membrane?
>

If you are using the ff53a6 FF then you need to add the appropriate lipid
parameters in the ffnonbonded.itp and ffbonded.itp files (of ff53a6 FF)
files which is very well explained in the tutorial. Then in your .top file
you need to include the DPPC.itp. However, if you are using CHARMM36 FF,
then you can directly use pdb2gmx on your system (I suppose DPPC is already
included in it). If you wish to use the ff43a1 FF, then you can find the
modified .itp files at
https://sites.google.com/site/anirbanzz/gpcr-gromacs-tutorial .


> 2)Furthermore, the lipid molecules are listed in my pdb file  with the
> abbreviation "DPP", whereas I see that those ones are called "DPPC" in the
> Tutorial. Therefore, Should I replace "DPP" abbreviation with "DPPC" in my
> pdb file? Could this difference cause any bugs in the next steps?
>

PDB files use three letter convention for residue names. I think you can
change them without any issue in the .gro file.

-Anirban


> Any suggestion would be appreciated,
>
> Silvia
>
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