On 11/26/16 2:41 PM, Jonathan Phillips wrote:
Hi,
I'm trying to run a simulation of a protein:ligand complex using chamm27
and cgenff2b7. After a little hacking (I'm using a PRES), I've used
charmm2gromacs-pvm.py to convert cgenff2b7 to cgenff2b7.ff/, and then
combined that with the charmm27 forcefield that comes with gromacs.
FWIW, we have a complete CHARMM36 + latest CGenFF available at our website to
save you some pain: http://mackerell.umaryland.edu/charmm_ff.shtml#gromacs
pdb2gmx runs without error, however when I run grompp, I get this:
Program grompp, VERSION 5.0.4
Source code file:
/var/tmp/portage/sci-chemistry/gromacs-5.0.4/work/gromacs-5.0.4/src/gromacs/gmxpreprocess/toppush.c,
line: 742
Fatal error:
Unknown bond_atomtype CG1N1
For more information and tips for troubleshooting, please check the GROMACS
website at http://www.gromacs.org/Documentation/Errors
I can't work out what bond_atomtype is, or exactly where I've been stupid.
"bond_atomtype" means "an atom type used in a bonded interaction."
I've checked that:
atomtypes.atp contains the following line
CG1N1 12.01100 ; for cyano group
(if it's relevant, this was generated by appending the cgen atomtypes file
to the charmm atomtypes file).
ffcgenbonded.itp contains the following lines (under the [ bondtypes ]
section)
CG1N1 CG2R61 1 0.1435 288696.0
CG1N1 CG331 1 0.147 334720.0
CG1N1 NG1T1 1 0.118 881150.4
charmm27cgen.ff/forcefield.itp contains
#include "ffcgenbonded.itp"
topol.top contains
#include "./charmm27cgen.ff/forcefield.itp"
grompp is being called with -p topol.top
All bonds containing a CG1N1 atom in cgen.rtp are to one of the three
atomtypes in ffcgenbonded.itp quoted above.
Also, my ligand doesn't contain residues that have a CG1N1 atom in them
(neither does my protein, surprise, surprise).
So I don't know why it's looking at CG1N1, and I don't know why there are
issues with this atomtype, and I don't know what a bond_atomtype is, which
leaves me rather stuck.
Does anybody have any suggestions?
The presence of an atom type in the .atp file is not enough. That file is only
ever read by pdb2gmx. grompp needs parameters for all those atom types in
ffnonbonded.itp. So if it finds a bonded interaction that involves an atom type
it doesn't know about (e.g. you have a type in ffbonded.itp but not
ffnonbonded.itp, which I bet is the case here) you get a fatal error.
-Justin
--
==================================================
Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow
Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 629
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201
jalem...@outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul
==================================================
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