AqpM channel water occupancy. Water occupancy histograms for the four AqpM monomers (M1-M4) are shown. The number of water molecules inside the constriction region of each AqpM monomer was determined for 10,000 snapshots separated by 2 ps taken from the 20 ns simulation. The average occupancy n of each monomer is displayed on the upper-left corner of each panel. The histograms show that the four monomers have an average of 7±1 water molecules inside the constriction region.