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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TLDR
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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Integrated operando X-ray absorption and DFT characterization of Cu–SSZ-13 exchange sites during the selective catalytic reduction of NOx with NH3
Jean-Sabin McEwen,Trunojoyo Anggara,William F. Schneider,Vincent F. Kispersky,Jeffrey T. Miller,W. N. Delgass,Fabio H. Ribeiro +6 more
TL;DR: In this paper, the authors investigate the Cu oxidation state and coordination environment in copper-exchanged chabazite (Cu-SSZ-13) under operando conditions representative of NO x selective catalytic reduction (SCR) with ammonia, using a combination of X-ray absorption spectroscopy (XAS) experiments, density functional theory (DFT), and first-principles thermodynamics models.
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Wired Porous Cathode Materials: A Novel Concept for Synthesis of LiFePO4
Robert Dominko,Marjan Bele,Jean-Michel Goupil,Miran Gaberscek,Darko Hanzel,Iztok Arčon,Janez Jamnik +6 more
TL;DR: In this paper, the authors demonstrate a sol−gel-based route that leads to large (up to 20 μm) primary LiFePO4 particles, each of which contains hierarchically organized pores in the meso and macro range.
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Time-dependent density functional calculations of ligand K-edge X-ray absorption spectra
TL;DR: In this article, a TD-DFT-based protocol was used to simulate the Cl K-edge spectra of a series of metal tetrachloride complexes and the influence of the chosen density functional, relativistics, basis set, and solvation has been systematically investigated, showing that good agreement between the calculated spectra and the relative experimental energies and intensities can be achieved by using the BP86 functional with standard polarized triple-ζ basis sets (such as the TZVP basis of Ahlrichs and co-workers).
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Biological Methane Oxidation: Regulation, Biochemistry, and Active Site Structure of Particulate Methane Monooxygenase
TL;DR: This review summarizes for the first time the often controversial pMMO literature, focusing on recent progress and highlighting unresolved issues.
Journal ArticleDOI
Spectroscopic and computational insight into the activation of O2 by the mononuclear Cu center in polysaccharide monooxygenases
Christian H. Kjaergaard,Munzarin F. Qayyum,Shaun D. Wong,Feng Xu,Glyn R. Hemsworth,Daniel J. Walton,Nigel A. Young,Gideon J. Davies,Paul H. Walton,Katja Salomon Johansen,Keith O. Hodgson,Britt Hedman,Edward I. Solomon +12 more
TL;DR: The solution structures of both the reduced and oxidized Cu site are determined, and it is determined how this site is capable of facile O2 activation by a thermodynamically difficult one-electron reduction, via an inner-sphere Cu-superoxide intermediate.
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