[gmx-users] Error when performing grompp on lipid bilayer modeled with CHARMM27

[Jackson Chief]

I want to make a model of a GPCR inserted into lipid bilayer.  I obtained
the structure file for a solvated POPC bilayer from the CHARMM-GUI site.  I
used CHARMM27 force field to model the bilayer and *pdb2gmx *had no problem
generating the *.gro, *.top, and posre.itp files.  When I perform *grompp* I
receive the following warning and error;

"WARNING 1 [file ffnonbonded.itp, line 130]:
  Overriding atomtype HOL"

"ERROR 1 [file bilayer.top, line 271489]:
  No default U-B types"

I though that the issue with creating Urey-Bradley interactions using *pdb2gmx
*had been corrected in Gromacs-4.5.4.  Please give me some advice on how to
proceed further.

Thank you,
Jackson Chief Elk
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