[gmx-users] change in secondary structure after npt equilibration

Justin A. Lemkul jalemkul at vt.edu
Fri Jan 28 14:10:42 CET 2011



bharat gupta wrote:
> Thanks for the advice ... I have checked all the equilibration graphs 
> and they have converged well... I want to know one more thing about the 
> anaylsis of simulation result.... I want to know whether the water 
> molecules are entering in the protein molecule or not and if so how to 
> track down those specific water molecules .. ( since I am simulating a 
> GFP which is well protected from water and I have made some changes in 
> the structure of GFP and then simulating it to see how this leads to 
> change in protein structure ?? )
> 

Watching the trajectory is the first step.  There may be ways to quantify these 
water molecules, using e.g. g_select or perhaps trjorder, but I can't say that I 
actually know how to do that.  I've never had to try :)

-Justin

> On Fri, Jan 28, 2011 at 5:00 AM, Justin A. Lemkul <jalemkul at vt.edu 
> <mailto:jalemkul at vt.edu>> wrote:
> 
> 
> 
>     sonali dhindwal wrote:
> 
>         Hi Justin,
> 
>         I am writing in this correspondence, because I also had the same
>         query once that secondary structure changes after equilibration,
>         and you are right that visualisation programs are not always
>         reliable.
>         You also mentioned this time that we should check wether
>         equilibration sufficiently converged all of the thermodynamic
>         observables. It will be very kind of you if you can throw some
>         light in this regard that how these observables should be checked.
> 
> 
>     Presumably, you've chosen an ensemble (NVT, NPT, etc) that
>     represents some set of desirable conditions.  You have to make sure
>     that properties like temperature, pressure, density, energy, etc
>     have converged, otherwise the system is not yet equilibrated under
>     those conditions.
> 
>     -Justin
> 
>         Thanks and Regards
> 
>         -- 
>         Sonali Dhindwal
> 
>         “Live as if you were to die tomorrow. Learn as if you were to
>         live forever.”
> 
> 
>         --- On *Fri, 28/1/11, Justin A. Lemkul /<jalemkul at vt.edu
>         <mailto:jalemkul at vt.edu>>/* wrote:
> 
> 
>            From: Justin A. Lemkul <jalemkul at vt.edu <mailto:jalemkul at vt.edu>>
>            Subject: Re: [gmx-users] change in secondary structure after npt
>            equilibration
>            To: "Discussion list for GROMACS users"
>         <gmx-users at gromacs.org <mailto:gmx-users at gromacs.org>>
>            Date: Friday, 28 January, 2011, 5:53 PM
> 
> 
> 
> 
>            bharat gupta wrote:
>             > Hi,
>             >
>             >
>             > I am doing a simulation of a 230 amino acid protein for
>         3ns ...
>            and I have completed the npt equilibration step .. After
>         retrieving
>            the structure from npt step and viewing it in pymol, reveals that
>            some portion of the beta strand got changed to a loop but when I
>            visualized the same structure in VMD I found that nothing has
>            happened to the structure .. In order to confirm more ... I
>            generated the SS profile using dssp and I found that , the dssp
>            shows E i.e. sheet for that region .. So what shall i do next ...
>            shall I continue with the production step or not ??
>             >
> 
>            Visualization programs are not always reliable in what they show
>            you, we've discussed that.  Methods like DSSP and STRIDE are far
>            more trustworthy, and seem to indicate that your structure is
>         fine.     What you should be much more concerned with at this
>         point is whether
>            or not your equilibration sufficiently converged all of the
>            thermodynamic observables.
> 
>            -Justin
> 
>             > -- Bharat
>             > Ph.D. Candidate
>             > Room No. : 7202A, 2nd Floor
>             > Biomolecular Engineering Laboratory
>             > Division of Chemical Engineering and Polymer Science
>             > Pusan National University
>             > Busan -609735
>             > South Korea
>             > Lab phone no. - +82-51-510-3680, +82-51-583-8343
>             >
>             > Mobile no. - 010-5818-3680
>             > E-mail : monu46010 at yahoo.com <mailto:monu46010 at yahoo.com>
>         </mc/compose?to=monu46010 at yahoo.com <mailto:monu46010 at yahoo.com>>
>            <mailto:monu46010 at yahoo.com <mailto:monu46010 at yahoo.com>
>         </mc/compose?to=monu46010 at yahoo.com <mailto:monu46010 at yahoo.com>>>
> 
>             >
> 
>            -- ========================================
> 
>            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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> 
>     -- 
>     ========================================
> 
>     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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> 
> 
> 
> -- 
> Bharat
> Ph.D. Candidate
> Room No. : 7202A, 2nd Floor
> Biomolecular Engineering Laboratory
> Division of Chemical Engineering and Polymer Science
> Pusan National University
> Busan -609735
> South Korea
> Lab phone no. - +82-51-510-3680, +82-51-583-8343
> Mobile no. - 010-5818-3680
> E-mail : monu46010 at yahoo.com <mailto:monu46010 at yahoo.com>
> 

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

Justin A. Lemkul
Ph.D. Candidate
ICTAS Doctoral Scholar
MILES-IGERT Trainee
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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