[gmx-users] get a box of 100 molecules

Justin A. Lemkul jalemkul at vt.edu
Fri Mar 13 15:57:38 CET 2009



Adrien Delmont wrote:
> What are the suitable options for  Chirality  , Full charges ,  Energy 
> Minimization in PRODRG  to get input files  for hydrocarbon molecules ? 
> And If I choose Full charges : YES , I will get the files that include 
> charge info. Can I erase the charge info and  write the charge info I 
> got from Gaussian ( net charge is zero ) according to the order of atoms 
> that I paste to the PRODRG screen ? Could you give me some advices about 
> this ?
> 

Chirality probably has to do with stereospecificity.  I have never messed with 
it.  I figure, if I've got a stereospecific molecule, then yes, preserve 
chirality.  If the molecule is achiral it shouldn't matter.

If you're going to replace the charges (which is a good idea!) then the 
full/reduced point is moot.  I believe it has to do with the phase of the 
molecule (condensed or vacuum).  Simply use a text editor to adjust them in the 
output topology.

EM: do you want the coordinates minimized, or not?  Choose "No" if your ligand 
is from a docked structure, you will want to do EM with the molecule in the 
complex.  If not, then you can choose "Yes" or "No" depending on what you feel 
is necessary.

-Justin

> Thanks in advance
> 
> Adrien
> 
> ------------------------------------------------------------------------
> *From:* Justin A. Lemkul <jalemkul at vt.edu>
> *To:* adriendelmont at yahoo.com; Discussion list for GROMACS users 
> <gmx-users at gromacs.org>
> *Sent:* Thursday, March 12, 2009 12:17:57 AM
> *Subject:* Re: [gmx-users] get a box of 100 molecules
> 
> 
> 
> Adrien Delmont wrote:
>  > If I create an .rtp file for my molecule how can I use this file when 
> I producing gro and top files and Can I use this .rtp file with oplsaa 
> and gromos 96 force fields for two different md run successfuly ? 
> Because I plan to run md simulations for all atom and united atom force 
> fields and compare the results. Secondly If I use PRODRG , the only 
> force field I can use is oplsaa. Is it true ? Can't I use a gromos 96 
> force field ?
>  >
> 
> I think you should start by reading the manual about .rtp files and how 
> they are used.  Each force field has its own .rtp, so no, you cannot use 
> the same .rtp file with different force fields.  Make a local copy (in 
> your working directory) if you choose to modify your .rtp files; if you 
> are unsure of what you are doing you can seriously screw things up.
> 
> PRODRG produces Gromos-compatible force fields, not OPLS; this is 
> answered in the FAQ at the PRODRG site.
> 
> I reiterate: read the manual, be comfortable with how the file types are 
> used, then proceed.
> 
> -Justin
> 
>  > --- On *Wed, 3/11/09, 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] get a box of 100 molecules
>  >    To: "Gromacs Users' List" <gmx-users at gromacs.org 
> <mailto:gmx-users at gromacs.org>>
>  >    Date: Wednesday, March 11, 2009, 9:53 PM
>  >
>  >    Adrien Delmont wrote:
>  >    > The molecule I use is a simple hydrocarbon ( n-heptane ) and I 
> think that
>  >    I should add something like  dihedral, bond, angle parameters 
> after I search the
>  >    literature. I found some information about that. I think I will 
> add parameters
>  >    into the related force fields .itp file. Is it true ? And then I 
> will create a
>  >    box of 100 molecules without any error.
>  >    >
>  >    Most (if not all) of the parameters you will need will already be 
> present in
>  >    the force field.  No modification of any of these files should be 
> necessary..  If
>  >    you want to use pdb2gmx to create your topology, you need to 
> create an .rtp
>  >    entry. For a simple alkane (especially with a UA representation), 
> it should be
>  >    trivial to write the topology by hand with a text editor and a 
> thorough
>  >    understanding of Chapter 5.
>  >
>  >    Alternate ideas:
>  >
>  >    1. Use PRODRG to generate a rough topology. Verify its contents before
>  >    proceeding, make any modifications you need, and validate the 
> resulting
>  >    topology.
>  >    2. Don't use Gromos96.  AFAIK, none of the Gromos variants deal 
> very well
>  >    with hydrocarbon chains.  OPLS might be better, but I think there 
> are some
>  >    limitations there, too.
>  >
>  >    -Justin
>  >
>  >    > --- On *Wed, 3/11/09, 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] get a box of 100 molecules
>  >    >    To: adriendelmont at yahoo..com 
> <mailto:adriendelmont at yahoo..com>, "Discussion list for GROMACS
>  >    users"
>  >    >    <gmx-users at gromacs.org <mailto:gmx-users at gromacs.org>>
>  >    >    Date: Wednesday, March 11, 2009, 9:11 PM
>  >    >    >    Adrien Delmont wrote:
>  >    >    >  I just want to add missing parameters for my molecule in order
>  >    to get
>  >    >    ...gro and top files for example GROMOS96 43a2 force field . 
> How can I
>  >    add
>  >    >    missing parameters ? I didn't find any information about this
>  >    procedure.
>  >    >    I'm waiting for your help.
>  >    >    >      >    You'll have to define what you mean by 
> "parameters" - is
>  >    this
>  >    >    some new small molecule that has not been parameterized under 
> this
>  >    force field?    Are you starting from scratch?  If so, this is not 
> a trivial
>  >    problem for a
>  >    >    beginner. Read here:
>  >    >    >    http://wiki.gromacs.org/index.php/Parameterization
>  >    >    >    If you have adequate parameters for most of your 
> molecule and are
>  >    missing
>  >    >    something like a dihedral, etc. then read the primary 
> literature and
>  >    derive it
>  >    >    yourself.  This process is also complicated, but is probably 
> less work
>  >    than
>  >    >    coming up with parameters for a brand new molecule.
>  >    >    >    -Justin
>  >    >    >    > Thanks in advance
>  >    >    >    >    > --- On *Wed, 3/11/09, Mark Abraham
>  >    /<Mark.Abraham at anu.edu.au <mailto:Mark.Abraham at anu.edu.au>>/*
>  >    >    wrote:
>  >    >    >    >    From: Mark Abraham <Mark.Abraham at anu.edu.au 
> <mailto:Mark.Abraham at anu.edu.au>>
>  >    >    >    Subject: Re: [gmx-users] get a box of 100 molecules
>  >    >    >    To: "Discussion list for GROMACS users"
>  >    >    <gmx-users at gromacs.org <mailto:gmx-users at gromacs.org>>
>  >    >    >    Date: Wednesday, March 11, 2009, 4:58 PM
>  >    >    >    >    Adrien Delmont wrote:
>  >    >    >    >    >    >
>  >    >        
> ------------------------------------------------------------------------
>  >    >    >    > *From:* Adrien Delmont <adriendelmont at yahoo.com 
> <mailto:adriendelmont at yahoo.com>>
>  >    >    >    > *To:* jalemkul at vt.edu <mailto:jalemkul at vt.edu>
>  >    >    >    > *Sent:* Wednesday, March 11, 2009 6:09:53 PM
>  >    >    >    > *Subject:* Re: [gmx-users] get a box of 100 molecules
>  >    >    >    >    > I didn't get gro and top files with any
>  >    force field
>  >    >    in Gromacs. I
>  >    >    >    basicly want to use oplsaa and GROMOS96 43a2 force field
>  >    (improved
>  >    >    alkane
>  >    >    >    dihedrals) . I think I should add all the parameters 
> but  how
>  >    can I
>  >    >    add my
>  >    >    >    parametes both into oplsaa and GROMOS96 43a2 force field ?
>  >    >    >    >    You can't just mix force fields. See
>  >    >    >    http://wiki.gromacs.org/index.php/force_field
>  >    >    >    >    Mark
>  >    >    >    _______________________________________________
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>  >    >    >    -- ========================================
>  >    >    >    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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> -- ========================================
> 
> 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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-- 
========================================

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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