From: Jerry Xu (
Date: Thu Jul 15 2004 - 10:28:15 CDT

Hey, All:
   I saw somebody asked the same question a while ago but never got
response, since I met the same situation, so I just ask again here and
really hope somebody know how to resolve the problem and like to share the
tip---will really appreciate!!
   I use psfgen package in VMD to generate a PSF file for HIV-protease
(1a30.pdb), I delete all non-protein atoms and only choose chain A. When I
generate it as X-PLOR type (the default psf file type in psfgen), it has no
problem to be used by NAMD , but when I generate it as charmm type, it can
not be accepted by CHARMM----the error message is "maximum atom number
exceeded per group". I tried with other smaller proteins then found out it
seems psfgen just put all the atoms into one group. If the protein is small
(under 50-60 residues), it is still okay for CHARMM, but when protein is
little larger, CHARMM always complain too many atoms per group.
  Is here anyone know how to resolve the problem? I asked the guy who once
post the similar question---he never get any answer from this mail list and
just redo it with CHARMM....

Thanks again
Sincerely yours

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