[gmx-users] hydrogen pairs in POPG topology using gromos ff

[Gillams R.J.]

Dear all,
I am trying to simulate a atomistic POPG bilayer, using gromacs 4.0.7.
I have found models for POPG developed by both Zhao et al (based on burger lipids) and Kukol (GROMOS 53a6 lipids).
The PG head group contains two hydroxyl groups but for some reason the 1-4 non-bonded interactions of the hydrogen atoms are not included in the pairs section of either POPG topologies.
The headgroups of both POPG models are based upon the GROMOS propylene glycol topology, contributed to the GROMACS website by Dallas Warren, and this topology does contain the 1-4 interactions for these hydrogen atoms.
I cant seem to find any information about this in the Zhao et al, Kukol and GROMOS forcefield papers, so I was wondering if anybody could shed some light on the situation?
Thanks
Ric Gillams