The density profiles of the following beads were computed using the gmx density command: chloride (CL), phosphate (PO4 in the Martini models and P in the Kir2.2. The protein structure (PDB ID 6M84) was downloaded from the OPM database and processed with the Chimera Dock Prep tool 203 to add any missing atoms. The CG model of the protein was generated using martinize2 204 , version 0.9.6.