[gmx-users] Error with CHARMM36 force field

[laurenmr]

Hi Gromacs Users,

I have downloaded the latest version of the CHARMM36M force field. My 
aim is to compare a simulation using CHARMM36M and CHARMM36. In the 
forcefield.itp there is an 'if' statement allowing the user to switch to 
the old CHARMM36 force field by directing to the old cmap itp:

; Allow the user to specify CHARMM36 parameters, instead
; Default behavior is to use CHARMM36m
#ifdef USE_OLD_C36
#include "old_c36_cmap.itp"
#else
#include "cmap.itp"
#endif

However, when I include "define = -DUSE_OLD_C36" in my .mdp file I 
receive this error at the grompp command:

Fatal error:
An input file contains a line longer than 4095 characters, while the 
buffer passed to fgets2 has size 4095. The line starts with: 'C NH1 CT1 
C NH1 1 24'

Could anyone suggest a way around this or should I download an older 
version of CHARMM36 (before CHARMM36M)?

Thanks in advance for the help!

Lauren