[gmx-users] Simulation of membrane protein

[Mark Abraham]

On 02/11/11, James Starlight <jmsstarlight at gmail.com> wrote:

> Justin, Mark,
> 
> Ok
> not I've included posre only to the lipid.itp wich consist of parameters for just 1 lipid
> 
> #ifdef POSRES_LIPID
> #include "posre_lipid.itp"
> #endif
> 
> to the minim.mdp I've included
> define        = -DPOSRES_LIPID    ; position restrain the lipids
> 
> As the result I have not obtained any error in grompp but after minimization my lipid bilayer was perturbed. I've used very strong posres. Why it have not worked ?

 
We can't know, because we don't know what's in any files, nor why you think the bilayer was perturbed. If you would like useful help, you need to be exhaustive in your description of what you have done, what you have observed and what you think about those. It is easier for people who might volunteer free help to do something else with their time than to ask follow-up questions when few details were given originally.
 
Mark 
 

> 
> 
> 
> 
> 2011/10/31 Justin A. Lemkul <jalemkul at vt.edu>
> 
> 
> > 
> > 
> > 
> > 
> > 
> > James Starlight wrote:
> > 
> > 
> > > I've done all of that
> > > i have "posre_lipid.itp" - for 1 lipid ( posres for each of 50 atoms )
> > > 
> > > 
> > > I've included this in the topology of the bilayer
> > > 
> > > ; Include chain topologies
> > > #include "gromos53a6_lipid.ff/forcefield.itp"
> > > #include "dppc.itp"
> > > 
> > > ; Include water topology
> > > #include "gromos53a6_lipid.ff/spc.itp"
> > > 
> > > ; Include ion topologies
> > > #include "gromos53a6_lipid.ff/ions.itp"
> > > 
> > > #ifdef POSRES_LIPID
> > > #include "posre_lipid.itp"
> > > #endif
> > > 
> > > ; System specifications
> > > [ system ]
> > > 128-Lipid DMPC Bilayer in water
> > > 
> > > [ molecules ]
> > > ; molecule name nr.
> > > DPPC 64
> > > SOL              1193
> > > SOL               690
> > > 
> > > 
> > > Also I've tried to make posre for whole system ( large posres ) but it also was finished with same error
> > > 
> > > Fatal error:
> > > [ file posre_lipid.itp, line 6 ]:
> > > Atom index (2) in position_restraints out of bounds (1-1).
> > > This probably means that you have inserted topology section "position_restraints"
> > > in a part belonging to a different molecule than you intended to.
> > > In that case move the "position_restraints" section to the right molecule.
> > > For more information and tips for troubleshooting, please check the GROMACS
> > > website at http://www.gromacs.org/Documentation/Errors
> > > 
> > > What's most true for such multy system. Generate posre only for 1 part or for whole system?
> > > 
> > > 
> > 
> > 
> > 
> > Position restraints can only be applied on a [moleculetype] basis.  Thus, order matters a lot, and the whole system cannot be restrained in one file.  See the example here:
> > 
> > http://www.gromacs.org/Documentation/Errors#Atom_index_n_in_position_restraints_out_of_bounds
> > 
> > As it stands now, the topology you've shown tries to apply lipid position restraints after the ions have been #included, which makes no sense at all.
> > 
> > 
> > 
> > 
> > -Justin
> > 
> > -- 
> > ========================================
> > 
> > Justin A. Lemkul
> > Ph.D. Candidate
> > ICTAS Doctoral Scholar
> > MILES-IGERT Trainee
> > Department of Biochemistry
> > Virginia Tech
> > Blacksburg, VA
> > jalemkul[at]vt.edu(http://vt.edu/) | (540) 231-9080
> > http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin
> > 
> > ========================================
> > -- 
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> 
> 
> 
> 

 
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