Hi , I am working on dimer metalloprotein system in which I want to apply distance restraints to restrain the distance of coordination bond between metal and Ligand oxygen but I can not understand what type of interactions as given in GROMACS should I use . I have applied distance restraints as follows but it does not work.

#ifdef disres

[intermolecular_interactions ]

[ distance_restraints ]

; ai aj type index type low up1 up2 fac

864 5363 6 1 1 0.00000 0.1900000 0.2160000 1.0

#endif

kindly guide.

Thanks in adavence