Vishal Agarwal wrote:
Dear Justin,

Thanks for replying. I guess it should be -O4 from the convention but have to look more deeply to figure out that. I am noticing a few more things in the ffG45a3.rtp, entries like +N in the bonds and angles section. Since there is no atom type N in the monomer, are these entries correct or another typo ?


Probably another typo, unless glucose suddenly contains nitrogen and no one notified the scientific community :) I would again suggest modifying the .rtp entry (in a local copy of the .rtp file), modeled after ffG53a6.rtp, since it appears to be more reliable. There is no need to alter the [atoms] section, but it appears some of the bonded directives need some work.

-Justin

Vishal


On Sun, Feb 7, 2010 at 1:18 PM, Justin A. Lemkul <[email protected] <mailto:[email protected]>> wrote:



    Vishal Agarwal wrote:

        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.


    Not to my knowledge.  As long as all of the expected atoms are
    there, you shouldn't have a problem.



               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 ?


    The problem comes from this line in ffG45a3.rtp:

     [ impropers ]
    ;  ai    aj    ak    al   gromos type
      C1    O5    -O    C2     gi_2

    Clearly the force field is expecting to assign an improper around
    carbon C1 using an "O" atom in a previous unit as a reference.  I
    think this may be a typo in the file.  The ffG53a6.rtp file has this
    line for the same improper:

      C1    O5    O1    C2     gi_2

    I think this is what was intended.  I do not know why the anomeric
    carbon would be using a previous residue as a reference for
    assigning an improper.  Perhaps this is a bug.  Make a local copy of
    ffG45a3.rtp and fix the line to make it look like the ffG53a6.rtp
    entry.  Please report back if this works; it may need to be fixed
    for a future release.

    -Justin


        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
               <[email protected] <mailto:[email protected]>
        <mailto:[email protected] <mailto:[email protected]>>
               <mailto:[email protected] <mailto:[email protected]>
        <mailto:[email protected] <mailto:[email protected]>>>> 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
                      <[email protected]
        <mailto:[email protected]> <mailto:[email protected]
        <mailto:[email protected]>>
               <mailto:[email protected]
        <mailto:[email protected]> <mailto:[email protected]
        <mailto:[email protected]>>>
                      <mailto:[email protected]
        <mailto:[email protected]>
               <mailto:[email protected]
        <mailto:[email protected]>>
                      <mailto:[email protected]
        <mailto:[email protected]>
               <mailto:[email protected]
        <mailto:[email protected]>>>>> 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
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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> <http://vt.edu>
        <http://vt.edu> | (540)

               231-9080

                  http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

                  ========================================

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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> <http://vt.edu> | (540)
        231-9080
           http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin

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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

    ========================================
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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

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