[gmx-users] restraints between two different molecules

[Rebeca García Fandiño]

Dear Gromacs users,
I am trying to apply some distance restraints between two different molecules in a Gromacs simulation. I have read different things in the Gromacs list, such as both molecules should be in the same [atomtype] section (which is not the case) and also something related to the use of "pull_ngroups = 2". But it is not clear to me, and I don´t know how could I do it, even if this is possible.
So, the question is...would it be possible to apply restraints between diferent molecules during a simulation?
Any help would be appreciated. 
Best wishes,

Dr. Rebeca Garcia
Santiago de Compostela University
Spain