[gmx-users] force field: heme group

[Ramachandran G]

Dear all,
       It is known that force field for the heme group doesn't exist
in gromacs. So i tried to use amber force fields(AMBER94, AMBER99,
AMBER99p, AMBER03, AMBERGS, AMBERGSs) by patching with my latest
gromacs version 4.0.5 but still it gives the error message

'Residue 'HEME' not found in residue topology database'

Can anyone help me how to solve this problem. Thanks for your help.
Rama