[gmx-users] constraints between protein ligand - metal chelation

[R.S.K.Vijayan]

Dear Gromacs users

I was wondering if there exists any technique that sets
distance restraint between specified ligand (atoms) and the protein(atoms)
in Gromacs.  I am simulating a system which contains metal ions coordinated
to the Ligand. I looked in to the mailing list and Gromacs manual and
figured out that  *genrster*  can be employed, to
set distance, position and dihedral restraints. Unfortunately i also
stumbled on the fact  that restraints between systems is not possible.

Since force fields are not good at handling chelation  between metal atoms,
i find that the metals drifting away from the coordinated  ligand atoms
during the course of simulation, hence i introduced position constraints
for the metal and ended up realizing  that the coordination distance
between the ligand and the metal exceeds the permissible range and the
angles between the chelating atoms gets distorted  and some coordinating
residues like Histidine and Aspartic  acid also moves away from the metal.

Hence, i was wondering if l anyone knows of any method (apart from
QM/MM) that can help to set distance restraints between the protein (metal
ion ) and the  ligand, also any suggestion that could help in handling
ligand metal chelation is welcomed.
    Thanking in advance


Regards

Vijayan.R
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