[gmx-users] unknown cmap torsion between atoms

ram bio rmbio861 at gmail.com
Tue Nov 1 04:16:19 CET 2011

Hi Mark,

Thanks for the response.
I have built this system (protein in popc bilayer using charmm GUI) and
submitted the total built system to pdb2gmx, is this the reason for having
unknown CMAP torsion while executing grompp, by the way pdb2gmx doesnot
show any error. Cant the charmm gui built system be used in gromacs with

Out of the 134 atoms for each  popc in the structure file  few initial
atoms were not matching in the lipids.itp file under charmmff folder, so i
changed the atom names in the lipid.itp under popc section to match with
atom names in the structure file, is that could be reason?

moreover, grompp also throws error as no default U-B types along with
unknown CMAP torsion.

Could you please diagnose where the problem exists in my procedure and let
me know.



On Mon, Oct 31, 2011 at 9:57 PM, Mark Abraham <Mark.Abraham at anu.edu.au>wrote:

> On 1/11/2011 1:24 PM, ram bio wrote:
>> Dear Gromacs users,
>> I have built a protein embedded in popc bilayer and executed pdb2gmx
>> using charmm27 ff on the system and the toplogy file was created without
>> errors, but when wanted to minimise the system with grompp i am getting an
>> error as : unknown cmap torsion between atoms 8377 8379 8381 8394 8397.
>> Could someone please explain me what this error mean and how to overcome
>> this.
> It means you are somehow using CMAP on a dihedral whose atom types do not
> have a known CMAP function - "unknown CMAP torsion". You need to do some
> detective work on those atoms and their types to work out why.
> Mark
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