David van der Spoel a écrit :
Stéphane Téletchéa wrote:
Hello,

I'm willing to simulate a membrane protein, and to gain lipid equilibration time, i'm using either Dr Tieleman's lipids or Dr Vattulainen's lipids (dppc 128 / dppc64).

In order to fully surround my protein, i need to enlarge those boxes to get at least 256 lipids (thus multiply the 64 lipids by 4).

To perform the enlargment, i used genconf:
genconf -f dppc64.pdb -o dppc256.pdb -nbox 2 2 1

But when i try to use the resulting dppc256.pdb, the system crashes (even if i try to fully minimize it first). I assume the problem arises from overlapping atoms while doing genconf but i thought this was the goal of the tool to be carefull about this.

I've been able to perform some dynamics (1 ns test systems) without problems if i do not use genconf ...

Is there any problem in my methodology ?
Is there a clever way to duplicate the starting lipids ?

I'm willing to do a full automated process for the lipids, this is why i did use genconf. I'm actually trying to build manually the lipid bilayer, but since i'm not sure whether i'll use dppc, dmpc, popc, i'm still searching for an automated method.

Thanks a lot in avdance for your answers,

Stéphane Téletchéa

are you sure all the lipids are in one piece?
if not you will have very large bond energies in the minimization


No, unfortunately, they are not ...

I should have mentionned this first.
I took the dppc64.pdb for Dr Tieleman's site, and then imaged it using editconf:

editconf -f dppc64.pdb -o dppc64_pbc.pdb -pbc

But unfortunately, some lipids are not imaged (at least 18, 25 and 53). I tried using trjconv but it needs a topol.tpr that i don't have :-(

Any hint ?

Stéphane

--
Stéphane Téletchéa, PhD.                  http://www.steletch.org
Unité Mathématique Informatique et Génome http://migale.jouy.inra.fr/mig
INRA, Domaine de Vilvert                  Tél : (33) 134 652 891
78352 Jouy-en-Josas cedex, France         Fax : (33) 134 652 901
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