Pawan Kumar wrote:
Respected Sir,

Greetings from Pawan.
Thanks for all your suggestions and help.
The solvation is completed and the system is neutralized.
The position restraint mdrun and final mdrun has worked out successfully without any warnings and errors this time. The structure after the final mdrun is not quite acceptable as the lipids have pulled apart and there is a huge gap between the two layers of the lipids. I have made the run for 5000 steps with dt = 0.002.
Any suggestions please.


There are several possibilities for why this is may be happening.

1. Were there gaps between the water and lipid headgroups? If so, the lipids may be pulling towards the solvent. Restrain the lipids and run an equilibration for a longer time. 2. 5000 steps is far too short to expect any realistic behavior for lipids. Equilibration can take upwards of 10-20 ns. 3. You haven't mentioned the contents of your .mdp file. Maybe you're doing something wrong. 4. Are you using Gromos/Berger or OPLS/converted Berger for your system? There have been so many of these questions from different users over the last few days that it's hard to keep track. If you are using OPLS/converted Berger you may have made a mistake in translating the C6/C12 parameters.

-Justin

Thanking you,

Yours sincerely,
Pawan

On Tue, Mar 31, 2009 at 5:50 PM, Justin A. Lemkul <jalem...@vt.edu <mailto:jalem...@vt.edu>> wrote:



    Pawan Kumar wrote:

        Respected Sir,

        Greetings from Pawan.
        Thanks for all your kind help and suggestions.
        I will work on this and ask you if I have further doubts.
        Is it fine if I use the perl code given in
        wiki.gromacs.org/membrane-simulations
        <http://wiki.gromacs.org/membrane-simulations>
        <http://wiki.gromacs.org/membrane-simulations> for solvation
        after the genbox step to remove extra waters from the
        hydrophobic part of the bilayer ?


    You mean the C program or shell script at
    http://wiki.gromacs.org/index.php/Membrane_Simulations?  Yes, either
    of those should be fine.

    -Justin

        Thanking you,

        Yours sincerely,
        Pawan

-- ========================================

        Justin A. Lemkul
        Graduate Research Assistant
        ICTAS Doctoral Scholar
        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

        ========================================




--
========================================

Justin A. Lemkul
Graduate Research Assistant
ICTAS Doctoral Scholar
Department of Biochemistry
Virginia Tech
Blacksburg, VA
jalemkul[at]vt.edu | (540) 231-9080
http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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