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
Formation of a Copper(II)–Tyrosyl Complex at the Active Site of Lytic Polysaccharide Monooxygenases Following Oxidation by H2O2
Alessandro Paradisi,Esther M. Johnston,Morten Tovborg,Callum R. Nicoll,Luisa Ciano,Adam Dowle,Jonathan McMaster,Y. Hancock,Gideon J. Davies,Paul H. Walton +9 more
TL;DR: It is proposed from the Marcus cross-relation that the active site tyrosine is part of a “hole-hopping” charge-transfer mechanism formed of a pathway of conserved tyrosines and tryptophan residues, which can protect the protein active site from inactivation during uncoupled turnover.
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Monomeric Metal Aqua Complexes in the Interlayer Space of Montmorillonites as Strong Lewis Acid Catalysts for Heterogeneous Carbon–Carbon Bond-Forming Reactions
TL;DR: Montmorillonite-enwrapped copper and scandium catalysts showed outstanding catalytic activities for a variety of carbon-carbon bond-forming reactions, such as the Michael reaction, the Sakurai-Hosomi allylation, and the Diels-Alder reaction, under solvent-free or aqueous conditions.
Journal ArticleDOI
Zn impacts Cu coordination to amyloid-β, the Alzheimer's peptide, but not the ROS production and the associated cell toxicity
Bruno Alies,Bruno Alies,Isabelle Sasaki,Isabelle Sasaki,Olivier Proux,Stéphanie Sayen,Emmanuel Guillon,Peter Faller,Peter Faller,Christelle Hureau,Christelle Hureau +10 more
TL;DR: While Zn(II) does alter Cu( II) binding to Aβ, this has no effect on (Aβ)Cu induced ROS production and associated cell toxicity.
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Characterization of Cu-ZSM-5 Prepared by Solid-State Ion Exchange of H-ZSM-5 with CuCl
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Journal ArticleDOI
Molecular and electronic structures of mononuclear iron complexes using strongly electron-donating ligands and their oxidized forms.
Julia B. H. Strautmann,Serena Debeer George,Eberhard Bothe,Eckhard Bill,Thomas Weyhermüller,Anja Stammler,Hartmut Bögge,Thorsten Glaser +7 more
TL;DR: The ligand L (2-) is capable of providing a flexible coordination geometry with two binding sites for substrates and the allocation of two oxidation equivalents on the ligand, which implies that the molecular structures of the solid states are retained in solutions of nonpolar aprotic solvents.
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