[gmx-users] pulling of a molecule through protein-membrane system

[Alex Mathew]

Dear all gromacs users,

I would like to build a protein-membrane system to perform umbrella
simulation; I need to calculate the molecule transportation by pulling it
from top to bottom. In the tutorial, it says  "Some force fields include
everything you need. For instance, it is unwise to try to literally follow
this approach for a force field like CHARMM36, as it needs no modification.
In that case, you are much better off building the system with CHARMM-GUI
<http://www.bevanlab.biochem.vt.edu/Pages/Personal/justin/gmx-tutorials/membrane_protein/www.charmm-gui.org>
.

I want to use Charmm36 force field, but I did not see any option to make a
box for US (as mentioned in US tutorial). Any suggestion how should I
proceed?