Figure 13.

Feasible proton uptake/pumping processes connecting with the movement of water molecules in the DNC during the P_R → F transition based on our current Models (M) 1-3 calculations. The 2H₂O represents HOH604 and HOH608. In M1, the two water molecules are within the DNC H-bonded to the OH⁻ or H₂O Cu_B²⁺ ligands close to the positions observed in the X-ray crystal structure 3S8G.¹⁴ In M2, the 2H₂O are shifted to the upper water pool of the DNC. In M3, the water molecule that is a ligand of Cu_B²⁺ in M2, now dissociates from Cu_B²⁺ but still has H-bonding interaction with the ligand O²⁻. Figure is adapted with permission from Figure 4 of Ref 58, copyright © 2018 American Chemical Society.