[gmx-users] Amber-GS-S force field in Gromacs 4.5.1

[Lutz Maibaum]

Hello all,

I noticed significant changes in my simulation results between running gromacs 4.5.1 with the included amber-gs-s force field and gromacs 4.0.7 with Eric Sorin's amber ports. I eventually figured out that the parameter files in the amberGS.ff directory are identical (up to whitespace and comments) to those of the amber99sb force field. For example:

$ diff amberGS.ff/ffbonded.itp amber99sb.ff/ffbonded.itp 
366c366
< CK  CB  N*  CT       4      180.00     4.18400     2    ;
---
> CK  CB	N*  CT	     4      180.00     4.18400     2    ;

Is it possible that the parameter files got mixed up? If I understand correctly, amber-gs-s should be amber-94 without backbone dihedral potentials and without 1-4 scaling.

Thanks,

  Lutz