RE: vmd-l: incompatibility between VMD & NAMD for reading Amber crd files

From: Kamp, Marc vander (
Date: Mon Jun 21 2004 - 14:39:05 CDT

Hello John,
It is actually really a crd file that I'm reading into VMD (just the number of atoms followed by all coordinates, without any other info). I read in a amber parmtop file first, and then the crd file that holds coordinates for this parmtop-file.
(The text-commands in VMD are the following:
vmd > mol new test.parm7
vmd > mol addfile test.crd )
In the display, you immediately see that the number of atoms is mistaken for a coordinate, because there is one atom far from all others. And as I said, by deleting the first empty line in the crd file, the problem is solved and the correct structure is displayed.
It shouldn't be to hard to correct such a thing in VMD, should it? (Although I do not know anything about the VMD source code...)

        -----Original Message-----
        From: John Stone []
        Sent: Mon 21-6-2004 16:58
        To: Kamp, Marc vander
        Subject: Re: vmd-l: incompatibility between VMD & NAMD for reading Amber crd files

          It sounds like you are trying to load restart files, not 'crd' files.
        VMD supports the new restart file format used by Amber 7, but not the
        old version of the format. The 'crd' reader in VMD reads trajectory files
        only, and does not read the restart files. The organization of the various
        Amber file formats is unwieldy for VMD as there's no decent way to detect which
        type of file it is a priori. That being said, I do think we can make some
        improvements to the way VMD reads the various Amber files, at some expense
        in performance. If you're working with Amber 7 files, try loading your
        structure using the 'rst7' plugin and let me know if you still have trouble.
          John Stone

        On Mon, Jun 21, 2004 at 02:33:11PM +0200, Kamp, Marc vander wrote:
> Dear all / VMD-developers,
> I am using amber-type parameters in namd. I create the AMBER format input files using the tleap-program (which is included in the NAB-distribution available from the Case-group).
> The parmtop file can be read in into VMD without a problem (if you use the parm7 extension the file is automatically recognised) but reading in the crd file as was created by tleap doesn't go well; VMD reads the number of atoms as the first coordinate. This can simply be solved by deleting the first empty line of the crd-file (which makes the number of atoms the first line).
> However, if you want to use the crd file as input coordinates in NAMD (using 'ambercoor'), the first line must be empty again (otherwise the coordinates are not correctly understood, leading to 'infinite' energies in minimization).
> Of course this is not a very urgent problem, but it would be nice if NAMD and VMD would treat crd files equally. As NAMD can directly use the crd-files that are created with AMBER-suite programs, it would in my opinion be best to change the crd-reading possibility in VMD.
> Best to you all,
> Marc
        NIH Resource for Macromolecular Modeling and Bioinformatics
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        University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
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