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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Journal ArticleDOI
Ultrafast Particle Size Reduction of Fe73.9Si15.5Cu1Nb3B6.6 by High-Energy Milling: Nb2O5 as a Marker of Permeability Enhancement and Magnetic Hardening
Jesús López-Sánchez,Elena Navarro,Aida Serrano,Cecilia Granados-Miralles,Adolfo del Campo,Adrián Quesada,Pilar Marín +6 more
TL;DR: A reproducible and fast method to obtain optimal particle sizes for competitive ultra-soft magnetic applications based on Fe73.9Si15.5Cu1Nb3B6.6-nanostructured part is presented in this paper.
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An X-ray absorption study on copper-containing AlPO4-5 for selective catalytic reduction of NOx by propene
Ian D. Burton,Justin S. J. Hargreaves,David G. Nicholson,Merete Hellner Nilsen,Michael Stockenhuber +4 more
TL;DR: In this article, a copper-containing AlPO4-5 was synthesised using copper(II) acetate as the copper source, and the results showed that in the former copper is contained in Cu(O)4 groupings which are linked to another Cu( O)4======group at a Cu⋯Cu distance of 2.93
Journal ArticleDOI
Selective Excited-State Dynamics in a Unique Set of Rationally Designed Ni Porphyrins
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In Situ XAFS, XRD, and DFT Characterization of the Sulfur Adsorption Sites on Cu and Ce Exchanged Y Zeolites
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Journal ArticleDOI
Application of X-ray absorption spectroscopy to the structural characterisation of monodispersed benzotriazole coatings on partly oxidised copper thin films
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