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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Chalcogen Impact on Covalency within Molecular [Cu3(μ3-E)]3+ Clusters (E = O, S, Se): A Synthetic, Spectroscopic, and Computational Study
Brian J. Cook,Gianna N. Di Francesco,Ricardo B. Ferreira,James T. Lukens,Katharine E. Silberstein,Brenna C. Keegan,Vincent J. Catalano,Kyle M. Lancaster,Jason Shearer,Leslie J. Murray +9 more
TL;DR: This result highlights that the metal-ligand covalency is not reserved for more formally oxidized metal centers but rather is a significant contributor even at more typical ligand-field cases (i.e., Cu3II/II/I + E2-).
Journal ArticleDOI
XAFS studies on copper(I) complexes containing scorpionate ligands
TL;DR: In this article, the local structure of copper complexes containing scorpionate ligands has been investigated using X-ray Absorption Spectroscopy (XAS) and the GNXAS analysis has permitted the identification of the local environment of the copper site.
Journal ArticleDOI
XAFS study of aqua (diethylenetriamine)(isonicotinato)-copper(II) complex – inference of square-pyramidal geometry
TL;DR: In this paper, the X-ray absorption near edge structure (XANES) spectrum of aqua (diethylenetriamine) (isonicotinato) copper(II) complex has been compared with those of the standard compounds to estimate the coordination geometry and oxidation state of copper.
Journal ArticleDOI
CuFeAl-composite catalysts of oxidation of gasification products of solid fuels: In situ XAS and XRD study
Andrey A. Saraev,Anna M. Tsapina,A. V. Fedorov,Alexander L. Trigub,Olga A. Bulavchenko,Zakhar S. Vinokurov,Ya. V. Zubavichus,V. V. Kaichev +7 more
TL;DR: In this paper, the reduction of high-active FeAl and CuFeAl composite catalysts was investigated in situ by XRD and XAS in the temperature range between 100 and 600°C.
Journal ArticleDOI
Cu(I) and Cu(II) Complexes Based on Lonidamine-Conjugated Ligands Designed to Promote Synergistic Antitumor Effects
Fabio Del Bello,Maura Pellei,Luca Bagnarelli,Carlo Santini,Gianfabio Giorgioni,Alessandro Piergentili,Wilma Quaglia,Chiara Battocchio,Giovanna Iucci,Irene Schiesaro,Carlo Meneghini,Iole Venditti,Nitya Ramanan,Michele De Franco,Paolo Sgarbossa,Cristina Marzano,Valentina Gandin +16 more
TL;DR: In this paper , the authors used Synchrotron radiation-based complementary techniques [X-ray photorlectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS)] to characterize the electronic and molecular structures of the complexes and the local structure around the copper ion in selected complexes.
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