Modification of dihedral torsion potential

GROMACS version: any
GROMACS modification: no

Dear GROMACS users,

Is it possible to use dihedral restrains to make the rotation along phy/psy angles in one direction easier than in another?

OR

How one can modify a force field to do it?

Thanks in advance,

Harutyun Sahakyan

Senior Assistant at Laboratory of
Computational Modeling of Biological Processes,
Institute of Molecular Biology, NAS RA
7 Hasratyan St, Yerevan, Armenia
Tel: +374 93 323990
E-mail: h_sahakyan@mb.sci.am