Design and synthesis of model systems for oxygen binding and activation in dinuclear copper proteins.

Abstract

Following the spectroscopic1,2 and crystallographie3,6 characterization of the dinuclear copper site of hemocyanin, the coordination chemistry of models for such sites was developed7,8. Nature employs the dinuclear copper site for binding of dioxygen, as found in the hemocyanins, the oxygen transport proteins of molluscs and arthropods. It is also employed in enzymes, such as tyrosinase9, and, in combination with copper ions representing other types of biological copper, lacease10 and ascorbate oxidase11, for the activation of dioxygen. Interestingly, protons and chloride ions affect the cooperativity of the oxygen binding by Panulirus interruptus (spiny lobster)12 and Limulus polyphemus (horseshoe crab)13 hemocyanin, respectively, whereas the aggregation of Octopus dofleini (Pacific octopus) hemocyanin subunits to form a functional unit is controlled by magnesium ions14. Recent crystal structures and spectroscopic studies5,6,15 of oxy- and deoxy-hemocyanin under a variety of circumstances have given indications that these effects may operate at the level of control of the Cu-Cu distance.