[gmx-users] Solvatebox from itp GAFF organic solvents and amber solute.

Justin Lemkul jalemkul at vt.edu
Wed Aug 5 20:08:17 CEST 2015

On 8/5/15 1:58 PM, Sharapa wrote:
> Constructing solvent from itp files and pdb provided from virtualchemistry, (not
> making water or methanol solventbox that seems to be well automatizised) seems
> to me to be most untrivial (probably due to luck of experience).

gmx insert-molecules -ci single_molecule.pdb -o box.pdb -box X -nmol N

will insert N molecules into a cubic box of X-nm edge length.  That is for pure 
solvent, and it's the same as the first step in creating a mixed solvent (which 
is then followed by another round of gmx insert-molecules to add the co-solvent).

> Taking topologies from amber seems to be more trivial procedure, with
> amb2gmx.pl, but is it independent from forcefield. Dont i have to specify in
> calculation GAFF ?, and if yes - i dont see it as typical Gromacs forcefield,
> should i make smth extra for enabling GAFF?

That depends on what the .itp files contain.  If they have a [defaults] 
directive, all the force field parameters, etc. then they're self-contained and 
can be used as-is, then you're done.  If they require parameters from some 
parent force field (more likely, since you're dealing with frcmod files), then 
you need to utilize them in the context of whatever parent force field you were 
using in AMBER:

#include (some AMBER force field)
#include (whatever your solvent .itp is)



> Thanks in advance,
> Dmitriy
> On 05.08.2015 19:38, Justin Lemkul wrote:
>> On 8/5/15 11:23 AM, Sharapa wrote:
>>> Dear Justin,
>>> Thanks a lot for your links.
>>> I looked them once again (i googled them for few times while i am stucked with
>>> this problem) and still do not understand how they can help me.
>>> I will try to go throw manual once again.
>> I don't understand what the problem is.  You say you have topologies and
>> coordinates, so what's missing?  You have coordinates for a single molecule,
>> but not a full box?  That's trivial to construct with gmx insert-molecules or
>> genconf -nbox. All of that is described in those links.
>> -Justin
>>> Best regards,
>>> Dmitriy
>>> On 05.08.2015 01:20, Justin Lemkul wrote:
>>>> On 8/4/15 12:09 PM, Sharapa wrote:
>>>>> Thanks a lot for fast answer.
>>>>> Yes, my fault, i didnt specify - i have coordinates for my molecule (from dft
>>>>> optimisation or from any other minimisation). And i have coordinates for
>>>>> equilibrated solvents from virtualchemistry. So i have coordinates, amber
>>>>> topologies for solute and itp for solvent. And no good ideas on combining them
>>>>> together in one solvatebox.
>>>> http://www.gromacs.org/Documentation/How-tos/Mixed_Solvents
>>>> http://www.gromacs.org/Documentation/How-tos/Non-Water_Solvation
>>>> -Justin
>>>>> On 04.08.2015 17:26, Justin Lemkul wrote:
>>>>>> On 8/4/15 10:45 AM, Sharapa wrote:
>>>>>>> Dear users and developers of Gromacs,
>>>>>>> I am new in MD in general and in Gromacs particulary.
>>>>>>> I want to make MD of small organic molecule in few organic solvents.
>>>>>>> My molecule containes Si and I made GAFF parameters for it. I would like to
>>>>>>> use
>>>>>>> GAFF in my simulation, expecting it to be not too bad for describing my
>>>>>>> system
>>>>>>> (that also contain pi-pi stacking).
>>>>>>> So far using ambertools I have .frchmod and prmtop files for my solute. I
>>>>>>> found
>>>>>>> .itp GAFF topology and .pdb GAFF Liquid structure files for solvents that
>>>>>>> i am
>>>>>>> interested in on http://virtualchemistry.org/ site. Nevetherless i still
>>>>>>> dont
>>>>>>> see the way how to create solvatebox with solute starting from data
>>>>>>> described
>>>>>>> above. I didn't found a tutorial describing similar procedures. If anyone
>>>>>>> can
>>>>>>> recommend me anything - i would be extremely thankful.
>>>>>> Because coordinates can't be built from topologies.  See
>>>>>> http://www.gromacs.org/Documentation/File_Formats/Coordinate_File#Sources for
>>>>>> ideas.
>>>>>> -Justin


Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441


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