[gmx-users] making topology file for infinite crystal

Vishal Agarwal vishal.iitian at gmail.com
Sun Feb 7 19:02:09 CET 2010


Dear Justin,

Thanks for replying.

pdb2gmx -f cellulose.gro
>>
>>
> So then your "cellulose.gro" contains all the atoms of GLCA monomers, named
> exactly as the force field expects them?  Have you checked against the .rtp
> entry?  What force field are you using?
>
> ;;
>
Should they be exactly in the same order as the rtp entry ? The atom type I
specified is definitely according to the standard convention of rtp entry. I
am using G45a3 as the force field.


>> I am getting the following error while using pdbgmx.
>>
>> "Fatal Error:
>> Atom -O not found in residue 2 while adding improper"
>>
>> Atom type "O" is actually not part of the GLCA residue. Only atom type OA
>> is part of GLCA residue.
>>
>
> pdb2gmx is complaining about an atom, not an atom type.  Somewhere in the
> .rtp file (probably within the [impropers] section, there should be a line
> specifying an atom named O that belongs to the preceding residue (hence the
> minus sign). None of my .rtp files are like this.  Did you create a custom
> .rtp entry?
>
> ;;
No I didnt create a custom rtp entry.

>
>  Do I need to modify the rtp entry to suit my system or does this error
>> corresponds to something else ?
>>
>>
> That will depend upon the answers to the above questions.  If you created
> the .rtp entry, then you'll have to fix the problem of naming mismatch.  If
> you're using the standard .rtp entry for the force field, then it's easier
> to modify your coordinate file to match the naming expected by the force
> field.
>
> ;;
The problem I am having is where to modify my coordinate file. The residue
doesnot contain a atom type 'O'.

Another curious question I have is suppose if I have another system where
the a monomer uint say GLCA (specified in rtp) is connected by a bridging
atom say Carbon. Do I need to create a new rtp entry for pdbgmx to work or
is there  a work around by specifying that carbon as a separate residue ?


Again thanks for replying.

Best,
Vishal

-Justin
>
>  Your help is appreciated.
>> Thanks,
>> Vishal
>>
>> On Sun, Feb 7, 2010 at 11:35 AM, Justin A. Lemkul <jalemkul at vt.edu<mailto:
>> jalemkul at vt.edu>> wrote:
>>
>>
>>
>>    Vishal Agarwal wrote:
>>
>>        Dear Mark,
>>
>>        What I meant over here is the missing oxygen  (-O) which pdbgmx
>>        complains about is not a part of .rtp entry. There is no such
>>        type of oxygen specified in any of the .atp entry of the
>>        forcefield I am using.
>>
>>
>>    The "-O" is not an atom type, it indicates an oxygen atom of a
>>    previous residue.  It is still not clear what it is you're doing or
>>    what the actual problem is. If you want a resolution, you'll have to
>>    do as Mark asked and post your command line and the actual error
>>    message.  Remember, you're asking for free help - you have to make
>>    it easy for us to help you.
>>
>>    -Justin
>>
>>        Vishal
>>
>>
>>        On Sun, Feb 7, 2010 at 4:54 AM, Mark Abraham
>>        <Mark.Abraham at anu.edu.au <mailto:Mark.Abraham at anu.edu.au>
>>        <mailto:Mark.Abraham at anu.edu.au
>>        <mailto:Mark.Abraham at anu.edu.au>>> wrote:
>>
>>           On 07/02/10 14:52, Vishal Agarwal wrote:
>>
>>               Dear All,
>>
>>               Can anyone help me how can I go about preparing the topology
>>               file for an
>>               infinite crystal of cellulose. I have prepared the .gro
>>        file for
>>               5X5X5
>>               unit cells of cellulose II using GROMACS utility and
>>        intend to apply
>>               periodic BC on it. It has a glucose molecule as building
>>        block
>>               (GCLA).
>>               When I try running pdbgmx, I get an error for extra
>> hydrogens
>>               (which is
>>               not there in itp file but is actually there in the original
>>               structure
>>               which I am using) and missing oxygen (-O).
>>
>>
>>           People who might help aren't at all interested in your
>>        description
>>           of the error message. If the contents of your head were
>> reliable,
>>           you wouldn't have seen the error in the first place, or would
>>        have
>>           solved the issue already. :-) Copy and paste your command
>>        line, and
>>           what seems to be the relevant part of the error.
>>
>>           To use pdb2gmx, you need .rtp file entries that correspond to
>>        your
>>           monomers. If not, you will not be able to use pdb2gmx to
>> generate
>>           your topology files.
>>
>>           Mark
>>           --    gmx-users mailing list    gmx-users at gromacs.org
>>        <mailto:gmx-users at gromacs.org>
>>           <mailto:gmx-users at gromacs.org <mailto:gmx-users at gromacs.org>>
>>
>>
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>>
>>
>>
>>        --        Regards
>>
>>        ***********************************************
>>        Vishal Agarwal
>>        Research Scholar
>>        University of Massachusetts, Amherst
>>        ***********************************************
>>        'Your only obligation in any lifetime is to be true to yourself."
>>                   ---Richard Bach
>>
>>
>>    --    ========================================
>>
>>    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
>>
>>    ========================================
>>
>>    --    gmx-users mailing list    gmx-users at gromacs.org
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>>
>>
>>
>> --
>> Regards
>>
>> ***********************************************
>> Vishal Agarwal
>> Research Scholar
>> University of Massachusetts, Amherst
>> ***********************************************
>> 'Your only obligation in any lifetime is to be true to yourself."
>>            ---Richard Bach
>>
>
> --
> ========================================
>
> 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
>
> ========================================
> --
> gmx-users mailing list    gmx-users at gromacs.org
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> Please search the archive at http://www.gromacs.org/search before posting!
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>



-- 
Regards

***********************************************
Vishal Agarwal
Research Scholar
University of Massachusetts, Amherst
***********************************************
'Your only obligation in any lifetime is to be true to yourself."
            ---Richard Bach
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