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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Catalysis and Electron Transfer in De Novo Designed Helical Scaffolds
TL;DR: This work showcases the versatility of alpha helices as scaffolds for metalloprotein design and the progress that is possible through careful rational design as it shows the invariance of carbonic anhydrase activity to site position and scaffold, refine the authors' cupredoxin models, and enhance nitrite reductase activity up to 1000-fold.
Journal ArticleDOI
Characterization of the Copper(II) Binding Sites in Human Carbonic Anhydrase II.
TL;DR: Using paramagnetic NMR techniques and X-ray absorption spectroscopy, an N-terminal Cu(2+) binding location is identified and information on the coordination mode of the CuA site in CA is collected, consistent with a four- to five-coordinate N- terminating copper(II) binding site.
Journal ArticleDOI
De novo design and characterization of copper metallopeptides inspired by native cupredoxins.
Jefferson S. Plegaria,Matteo Duca,Cédric Tard,Thomas J. Friedlander,Aniruddha Deb,James E. Penner-Hahn,Vincent L. Pecoraro +6 more
TL;DR: Observations showed that the designed metal binding sites lacked the necessary rigidity to enforce the appropriate structural constraints for a Cu(II) chromophore (EPR and UV-vis); however, the Cu(I) structural environment and the high positive potential of CuT1 centers were recapitulated within the α-helical bundle of α3D.
Journal ArticleDOI
Synchrotron X-ray imaging reveals a correlation of tumor copper speciation with Clioquinol's anticancer activity
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Journal ArticleDOI
Combining Valence-to-Core X-ray Emission and Cu K-edge X-ray Absorption Spectroscopies to Experimentally Assess Oxidation State in Organometallic Cu(I)/(II)/(III) Complexes
TL;DR: In this article , a series of organometallic copper complexes in formal oxidation states ranging from +1 to +3 have been characterized by a combination of Cu K-edge X-ray absorption (XAS) and VtC XES.
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