Structures of metal-buffering ligands that have been used in Zn(II) titration experiments. The pZn values were measured at ligand concentration = 10 μM, total Zn(II) concentration = 1 μM, pH = 7.0, I = 0.1, and 25 °C.241 Unlisted are carbonic anhydrase, pZn = 12.4, and a decidedly non-1:1 binding Zn(II) indicator Zinquin, pZn = 9.3.245