title: Direct Copper(III) Formation from O2 and Copper(I) with Histamine Ligation.
abstract: Histamine chelation of copper(I) by a terminal histidine residue in copper hydroxylating enzymes activates dioxygen to form unknown oxidants, generally assumed as copper(II) species. The direct formation of copper(III)-containing products from the oxygenation of histamine-ligated copper(I) complexes is demonstrated here, indicating that copper(III) is a viable oxidation state in such products from both kinetic and thermodynamic perspectives. At low temperatures, both trinuclear Cu(II)2Cu(III)O2 and dinuclear Cu(III)2O2 predominate, with the distribution dependent on the histamine ligand structure and oxygenation conditions. Kinetics studies suggest the bifurcation point to these two products is an unobserved peroxide-level dimer intermediate. The hydrogen atom reactivity difference between the trinuclear and binuclear complexes at parity of histamine ligand is striking. This behavior is best attributed to the accessibility of the bridging oxide ligands to exogenous substrates rather than a difference in oxidizing abilities of the clusters.
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: J Brannon
authors.initials: JB
authors.lastname: Gary
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Cooper
authors.initials: C
authors.lastname: Citek
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Brown
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Zare
authors.affiliation: Department of Chemistry and Biochemistry, California State University , Chico, California 95929, United States.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Wasinger
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: T Daniel P
authors.initials: TD
authors.lastname: Stack
mesh_terms: D000588:Amines / Q000737:chemistry; D002614:Chelating Agents / Q000737:chemistry*; D003300:Copper / Q000737:chemistry*; D006632:Histamine / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D013058:Mass Spectrometry; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics
chemical_list: D000588:Amines; D002614:Chelating Agents; D008024:Ligands; D010087:Oxides; D003300:Copper; D006632:Histamine; D010100:Oxygen