Journal ArticleDOI
X-ray absorption edge determination of the oxidation state and coordination number of copper: application to the type 3 site in Rhus vernicifera laccase and its reaction with oxygen
Lung Shan Kau,Darlene J. Spira-Solomon,James E. Penner-Hahn,Keith O. Hodgson,Edward I. Solomon +4 more
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In this paper, a normalized difference edge analysis is used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase.Abstract:
Cu X-ray absorption edge features of 19 Cu(I) and 40 Cu(II) model complexes have been systematically studied and correlated with oxidation state and geometry. Studies of Cu(I) model complexes with different coordination number reveal that an 8983-8984-eV peak (assigned as the Cu 1s ..-->.. 4p transition) can be correlated in energy, shape, and intensity with ligation and site geometry of the cuprous ion. These Cu(I) edge features have been qualitatively interpreted with ligand field concepts. Alternatively, no Cu(II) complex exhibits a peak below 8985.0 eV. The limited intensity observed in the 8983-8985-eV region for some Cu(II) complexes is associated with the tail of an absorption peak at approx. 8986 eV which is affected by the covalency of the equatorial ligands. These models studies allow accurate calibration of a normalized difference edge procedure which is used for the quantitative determination of Cu(I) content in copper complexes of mixed oxidation state composition. This normalized difference edge analysis is then used to quantitatively determine the oxidation states of the copper sites in type 2 copper-depleted (T2D) and native forms of the multicopper oxidase, Rhus vernicifera laccase. The type 3 site of the T2D laccase is found to be fully reduced and stable tomore » oxidation by O/sub 2/ or by 25-fold protein equivalents of ferricyanide, but it can be oxidized by reaction with peroxide. The increase in intensity of the 330-nm absorption feature which results from peroxide titration of T2D laccase is found to correlate linearly with the percent of oxidation of the binuclear copper site.« lessread more
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Journal ArticleDOI
Direct metal-carbon bonding in symmetric bis(C-H) agostic Nickel(I) complexes
Weiying He,Weiying He,D. Dawson Beattie,Hao Zhou,Hao Zhou,Eric G. Bowes,Laurel L. Schafer,Jennifer A. Love,Jennifer A. Love,Pierre Kennepohl,Pierre Kennepohl +10 more
TL;DR: In this article, the authors report on the unusual electronic structure of linear electron-rich d9 Ni(I) complexes with symmetric bis(C-H) agostic interactions.
Spectroscopic studies of peptidylglycine -hydroxylating monooxygenase: toward a mechanism of superoxide channeling
TL;DR: The discovery that substrate binding turns on CO and (by inference) 0,-binding activity at a second copper center in PHM has allowed us to suggest a completely new mechanism for oxygen activation and formation of the reactive peroxo intermediate.
Journal ArticleDOI
The role of cyanide in the removal of type 2 copper from laccase
TL;DR: A method for the removal of the type 2 copper from tree laccase under anaerobic reducing conditions is improved and a mechanistic model is developed that should form the basis for the development of methods for removing the type 1 copper from other related systems.
Book ChapterDOI
Studies on the State of Copper and the Formation of its Oxidic and Metallic Phases in Zeolite Cunay
TL;DR: In this article, a reduction to small metallic copper clusters was observed after co-addition of water vapour and hydrogen, demonstrating the important role of strong ligands like water in the reduction mechanism, enabling a controlled formation of copper clusters.
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