[gmx-users] CHARMM to Gromacs

[Alessandro.Maiorana at roma2.infn.it]

Hi,
I'm a physics' student of Tor Vergata university(Rome). I exploit Gromacs
by short time. I am trying to use the CHARMM27 force field to Gromacs, but
I have some problems. I readed your instructions from web address:
http://www.gromacs.org/component/option,com_docman/task,doc_details/gid,59/.

I followed the procedure, that is:
Step one: I converted CHARMM force field in ffcharmmbon.itp and
ffcharmmnb.itp, through the use of the script
"convert_charmm_to_gromacs.pl".
Step two: I placed ffcharmmbon.itp and ffcharmmnb.itp in
/usr/local/gromacs/share/gromacs/top.
Step three: I downloaded the charmm_gromacs.tar.gz.
Step four: I copied all files in the tar-file to
/usr/local/gromacs/share/gromacs/top.
Step five: I added this line "ffcharmm CHARMM 27" in FF.dat.
Step six: The 'pdb2gmx' command was run using the command:
"pdb2gmx -ter -f <filename>.pdb -o <filename>.gro -p <filename>.top" but
the following error message is coming:
Program pdb2gmx, VERSION 3.3.3
Source code file: ter_db.c, line: 85

Fatal error:
Reading Termini Database: expected 3 items of atom data in stead of 1 on line
       N      NH3        14.0027    -0.3000

I changed the format of ffcharmm-n.tdb comparing with the ffG43a1-n.tdb,
but the following error message is coming:
Program pdb2gmx, VERSION 3.3.3
Source code file: ter_db.c, line: 257

Fatal error:
Reading Termini Database: Expecting a header at line

Can you help me? I hope to have been clear. Thanks for the help you going
to gave me. See you soon.