Figure 6

The example of ion channel and the ion filter process. The channel protein modified from pentameric ligand gated ion channel (PDBID:3EHZ) is presented using Pymol. A. the protein is shown in ribbon and colored in blue and the yellow lines denote the polar residues composing of the pore region. The greens dots indicate the ions and the red dots mean water molecules. The orang dash squares indicate the pore and filter regions. B. the proposed ion selecting mechanisms: 1) ion are shelled with and the channel do not contain ions; 2) the ion with water shell enter into the channel; 3) the water shelling the ion will be fixed by the polar residues using hydrogen bonds; 4) after the coordination of the ion and water molecules are fix, the ion can easy go through the filter region and is stabilized with the filter residues; 5) the water molecules composing empty shell will release out from the pore region and the channel change to the empty state for next ions.