Representative snapshots of MthK, ions, and all water molecules within 3 Å of the SF, during an MD trajectory. (A) Time series of the simulation with SPD³⁺ at 0 mV from Fig. 6 A. (B) SPD³⁺ with N_L coordinated by T59-OH groups at the entry to the SF. (C) SPD³⁺ released from the SF, followed by a water molecule entering the SF. (D) Entry of a K⁺ ion from the bulk solution into the pore, past a SPD³⁺ molecule. (E) Entry of the K⁺ into the SF. Thus under these conditions, ions and water can enter the pore and SF with SPD³⁺ in the pore.