Rotation of a molecule using electric field

Dear GROMACS users,
I am trying to rotate a charged molecule using the external electric field. For instance, I restrained the N and C terminal atoms of the ala-arg-ala peptide and trying to rotate the charged side chain of the arginine. I tried configurations for the electric field, with different values for ω (the field was applied along the peptide backbone, for example, electric-field-x = 2.0 150 5 0), however, no rotation for the arginine sidechain was observed. Do you have any idea what I do wrong, and is it possible in principle to rotate a charged molecule, using the external electric field?

The charge is distributed quite evenly in the side chain so there will not be a net force on it.