[gmx-users] Membrane is shifted a lot during umbrella sampling

[sudipta]

Dear Gromacs Users/Developers,

I am facing problem for doing umbrella sampling simulation for the
transferring of a small peptide across a membrene in presence of electric
field. Moreover, the simulation was carried out at constant area. Martini
force field for protein, lipid and water was used for this simulation. The
electric field was applied along the -z direction across the membrane. The
problem, which I am facing is that the position of membrane is shifted a
lot during this this simulation. Moreover, I notice the shifting of
membrane is significantly enhanced when I apply high electric filed. I
don't have any clue for this shifting problem. If anyone have  idea to
arrest the shifting problem then please share it. A copy of my input file
is attached herewith.

Thanks in advance
Sudipta