Re: [AMBER] Internal dielectric constant and pmemd

From: Samaneh Ghassabi Kondalaji <saghassabikondalaji.mix.wvu.edu>
Date: Fri, 21 Apr 2017 09:36:17 -0400

Unfortunately the process I am simulating says otherwise from experimental
point of view. I determined the values and now I need to apply them to my
system.

On Fri, Apr 21, 2017 at 9:26 AM, Adrian Roitberg <roitberg.ufl.edu> wrote:

> Sam:
>
> you said that:
>
> "I need to change the dielectric constant of water in
> this droplet from 78.5 to 1 and at the same time preserve the vacuum."
>
> And what I am telling you is that the dielectric constant of your system
> is already equal to 1 for the water, so I do not understand what your issue
> is.
> There is nothing to change from 78.5 to 1, it is already 1.
>
> adrian
>
>
> On 4/21/17 9:21 AM, Samaneh Ghassabi Kondalaji wrote:
> > I understand what igb=6 does to my system in terms of dielectric
> > constant and I actually need the value of one as I am in vacuum, but Is
> > there ANY way in pmemd that I can have two different dielectric
> constants (
> > it seems unrealistic but it is what it has to be!).
> > Cheers,
> > Sam
> >
> > On Fri, Apr 21, 2017 at 9:14 AM, Adrian Roitberg <roitberg.ufl.edu>
> wrote:
> >
> >> The dielectric constant of your system will be ONE without you doing
> >> anything.
> >>
> >> The fact that you are using igb=6 immediately does that, and the fact
> >> that you have water molecules does not make any difference.
> >>
> >> adrian
> >>
> >>
> >> On 4/21/17 9:11 AM, Samaneh Ghassabi Kondalaji wrote:
> >>> Yes, it seems very confusing but my system is a peptide in a
> large
> >>> water droplet (~3.0 nm in diameter) present in vacuum and I need the
> >> water
> >>> molecules to leave the system gradually. I use igb=6 so I can use pmemd
> >> for
> >>> vacuum simulations. I need to change the dielectric constant of water
> in
> >>> this droplet from 78.5 to 1 and at the same time preserve the vacuum.
> >> Can I
> >>> just do it with dielec or I will need external, internal dielectric
> >>> parameters?
> >>> Best
> >>> Sam
> >>>
> >>> On Fri, Apr 21, 2017 at 8:04 AM, David Case <david.case.rutgers.edu>
> >> wrote:
> >>>> On Thu, Apr 20, 2017, Samaneh Ghassabi Kondalaji wrote:
> >>>>
> >>>>> I am performing a simulation that requires the change of
> internal
> >>>>> dielectric constant and of course the non-default values of intdiel
> are
> >>>> not
> >>>>> supported in pmemd. I was wondering if anyone has found a way around
> >> it?
> >>>>> Has there been a bugfix recently that fixes this? Is it possible to
> use
> >>>> the
> >>>>> dielct value of matching the desired intdiel but use a different
> >> extdiel
> >>>> or
> >>>>> the dielct parameter will override the extdiel? I am using pmemd and
> >>>> igb=6
> >>>>> to simulate a very large system in the gas phase and I am not going
> to
> >> be
> >>>>> able to use sander for my purpose.
> >>>> I am confused here: if you are using igb=6, the concepts of a
> "internal"
> >>>> and
> >>>> "external" dielectric don't come into play. Any values you tried to
> >> enter
> >>>> there would be ignored.
> >>>>
> >>>> ....dac
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> AMBER mailing list
> >>>> AMBER.ambermd.org
> >>>> http://lists.ambermd.org/mailman/listinfo/amber
> >>>>
> >>>
> >> --
> >> Dr. Adrian E. Roitberg
> >> University of Florida Research Foundation Professor
> >> Department of Chemistry
> >> University of Florida
> >> roitberg.ufl.edu
> >> 352-392-6972
> >>
> >>
> >> _______________________________________________
> >> AMBER mailing list
> >> AMBER.ambermd.org
> >> http://lists.ambermd.org/mailman/listinfo/amber
> >>
> >
> >
>
> --
> Dr. Adrian E. Roitberg
> University of Florida Research Foundation Professor
> Department of Chemistry
> University of Florida
> roitberg.ufl.edu
> 352-392-6972
>
>
> _______________________________________________
> AMBER mailing list
> AMBER.ambermd.org
> http://lists.ambermd.org/mailman/listinfo/amber
>



-- 
*Samaneh ghassabi kondalaji*
*PhD student in Chemistry*
*555 CRL, Chemistry department*
*West Virginia University *
*Morgantown, USA*
*E-mail: **saghassabikondalaji.mix.wvu.edu*
<saghassabikondalaji.mix.wvu.edu>
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Received on Fri Apr 21 2017 - 07:00:02 PDT
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