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
Reads0
Chats0
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
Citations
More filters
Journal ArticleDOI
X-ray absorption spectroscopic studies on copper-containing hydrotalcite
TL;DR: In this article, the XANES spectra have been used to determine the local environment of the copper ions, which is consistent with the octahedron, elongated by Jahn-Teller effects.
Journal ArticleDOI
On the nature of the Cu-rich aggregates in brain astrocytes.
Brendan Sullivan,Gregory Robison,Jenna Osborn,Martin Kay,Peter Thompson,Katherine M. Davis,Taisiya Zakharova,Olga Antipova,Yulia Pushkar +8 more
TL;DR: XRF imaging of Au-labeled lysosomes and ubiquitin demonstrates a lack of co-localization with Cu-rich aggregates suggesting they are not involved in a degradation pathway, and overall data suggest that Cu in aggregates is bound by either metallothionein-3 or a yet unknown protein similar to metallothsionein.
Journal ArticleDOI
Understanding and Optimizing the Performance of Cu‐FER for The Direct CH4 to CH3OH Conversion
Dimitrios K. Pappas,Elisa Borfecchia,Michael Dyballa,Michael Dyballa,Kirill A. Lomachenko,Andrea Martini,Andrea Martini,Gloria Berlier,Bjørnar Arstad,Carlo Lamberti,Carlo Lamberti,Silvia Bordiga,Silvia Bordiga,Unni Olsbye,Stian Svelle,Pablo Beato +15 more
TL;DR: From the in situ spectroscopies, structure‐activity relationships between the reducibility of Cu species and the CH3OH yield are established and a Cu threshold that needs to be surpassed is established.
Journal ArticleDOI
Elucidating the mechanism of heterogeneous Wacker oxidation over Pd-Cu/zeolite Y by transient XAS.
Jerick Imbao,Jerick Imbao,Jeroen A. van Bokhoven,Jeroen A. van Bokhoven,Adam H. Clark,Maarten Nachtegaal +5 more
TL;DR: A transient X-ray absorption spectroscopic investigation of the heterogeneous Wacker oxidation over Pd-Cu/zeolite Y coupled with kinetic studies and chemometric analysis demonstrates that copper is not only the site of oxygen activation, but is also involved in the formation of undesired carbon dioxide.
Journal ArticleDOI
X-ray Absorption Studies of the Cu-Dependent Phenylalanine Hydroxylase from Chromobacterium violaceum. Comparison of the Copper Coordination in Oxidized and Dithionite-Reduced Enzymes
TL;DR: Comparison of absorption edge data on the reduced enzyme with data from Cu(I) bis- and tris(1,2-dimethylimidazole) complexes suggests a pseudo-three-coordinate structure.
Related Papers (5)
ATHENA, ARTEMIS, HEPHAESTUS: data analysis for X-ray absorption spectroscopy using IFEFFIT.
Bruce Ravel,Matthew Newville +1 more