Copper type ii EPR

Galactose oxidase (GAO) contains a Cu(II)-ligand radical cofactor. The cofactor, which is autocatalytically generated through the oxidation of the copper, consists of a cysteine-tyrosine radical (Cys-Tyr• ) as a copper ligand. The formation of the cross-linked thioether bond is accompanied by a C-H bond scission on Tyr272 with few details known thus far. Here, we report the genetic incorporation of 3,5-dichlorotyrosine (Cl2 -Tyr) and 3,5-difluorotyrosine (F2 -Tyr) to replace Tyr272 in the GAOV previously optimized for expression through directed evolution...

The reactions of (Z)-3-aryl-2-(methylthio)-5-(pyridine-2-ylmethylene)-3,5-dihydro-4H-imidazol-4-ones (3) with CuCl2·2H2O in the presence of a reducing solvent (alcohol or dimethylformamide (DMF)) produce three types of Cu-containing compounds: two Cu complexes with a composition of CuII(3)Cl2 (4) and CuI(3)Cl (5) as well as a salt (3 + H)+CuICl2- (6) in a 4 : 5 : 6 ratio depending on the substituent at the N(3) nitrogen atom of the ligand moiety. In non-reducing solvents (dimethyl sulfoxide (DMSO) and CHCl3/acetone), only complexes 4 were formed, All three Cu derivatives (4, 5, and 6) were characterized by single-crystal X-ray diffraction, UV/vis spectroscopy, and electrochemistry data...

Type 1 copper (T1Cu) proteins play important roles in electron transfer in biology, largely due to the unique structure of the T1Cu center, which is reflected by its spectroscopic properties. Previous reports have suggested a correlation between a high ratio of electronic absorbance at ∼450 nm to that at ∼600 nm ( R = A 450 / A 600 ) and a large copper(II) hyperfine coupling in the z direction ( A z ) in electron paramagnetic resonance (EPR). However, this correlation does not have a clear physical meaning, nor does it hold for many proteins with a perturbed T1Cu center...

A putative laccase gene (lacG) from Geobacillus sp. JS12 was cloned and expressed as a fusion protein with six histidine residues in Escherichia coli BL21 (DE3) cells, and the protein was primarily found in inclusion bodies. The resulting insoluble proteins were solubilized with 6 M guanidine HCl and refolded using an on-column refolding procedure. Ni-chelation affinity chromatography found the laccase to be a 30 kDa monomeric protein. Spectrophotometry and electron paramagnetic resonance (EPR) analysis indicated LacG as a multi-copper oxidase, with the usual laccase copper sites, Type 1, 2, and 3 Cu(II)...

Cu-modified zeolites have enormous potential as the catalysts facilitating the conversion of methane to methanol. It becomes important to investigate the active sites and the reaction mechanisms involved. In this paper, several spectroscopic methods such as UV-vis diffuse reflectance spectroscopy (UV-vis DRS), pulse electron paramagnetic resonance (EPR), diffuse reflectance Fourier transform infrared spectroscopy, and solid-state (13 C MAS) NMR have been employed to characterize the state of the Cu sites and the intermediates formed during the catalyst activation and methane-to-methanol transformation on Cu/H-ZSM-5 zeolite with low (0...

Copper(II) complexes of type (NHC)CuX2 (X = OAc, Cl, Br, BF4 , and NO3 ) bearing monodentate N -heterocyclic carbenes (NHCs) were prepared by in situ decarboxylation of imidazolium carboxylates as a new synthetic methodology for Cu(II)-NHC complexes. In contrast to the classical deprotonation method, the decarboxylation protocol does not require anaerobic conditions and provides access to complexes with NHCs that are unstable as free carbenes such as N , N '-diisopropyl-imidazolylidene and N , N '-dimethyl-imidazolylidene...

A 2-D copper(ii)-based coordination polymer, [Cu(SCN)(hmp)]n CP (1), was crystallized via the slow evaporation method after the reaction of CuSO4 ·5H2 O, 2-pyridinemethanol (hmpH), sodium thiocyanate and sodium hydroxide in water for functional applications. CP (1) was characterized via elemental analysis, FTIR, PXRD, magnetic, EPR, crystallographic and TGA studies. The crystal structure and EPR data confirmed a square pyramidal geometry around the Cu(ii) ions. The topological analysis revealed that CP 1 has a {6^ 3} point symbol with a [6...

The multicomponent electron paramagnetic resonance spectra of the blood during healing of skin burned wounds treated with a new generation biodegradable dressings containing poly(lactide-co-glycolide) were analysed. The evolution of different types of paramagnetic centers in the blood with time of healing was determined. The EPR spectra of the blood samples at 230 K temperature were measured at 1, 10, and 21 days after burning of the pig skin. The EPR lines of the following paramagnetic centers: the high-spin Fe3+ in methemoglobin (line I), high-spin Fe3+ in transferrin (line II), and Cu2+ in ceruloplasmin and free radicals (line III) were observed in the X-band (9...

The electrostatic self-assembly reaction of the [Cu(HL)]2+ cation, where HL = 2-(2-aminoethylamino) ethanol, and the N3 - or [Fe(CN)6 ]4- anion leads to the formation of two coordination polymers with the general formula of [Cu6 (μ1,1 -N3 )6 (μ1,3 -N3 )2 (μ1,1,3 -N3 )2 (μ1,1,1,3 -N3 )2 (HL)2 ]n (1) and {[Cu(HL)]2 [Fe(CN)6 ]·H2 O}n (2), respectively. The resulting compounds have been structurally characterized by a single-crystal X-ray diffraction technique. Compound 1 possesses a rare 3D structure. It contains centrosymmetric hexanuclear repeating units, which act as six-connected nodes in the final network and copper(ii) ions are joined together by azide anions with four different types of bridging modes, μ1,1 , μ1,1,3 , μ1,1,1,3 , and μ1,3 ...

Eight heteroleptic nickel(II) and copper(II) complexes of the type [M(L14)(nap)2] (18), where L14 = 2-(1-(4-substitutedphenyl)ethylidene)hydrazinecarbothioamide, nap = naproxen and M = Ni(II) or Cu(II) have been synthesized and characterized. UV-Vis and EPR spectral studies showed distorted octahedral geometry around metal(II) ions. Cyclic voltammogram of complexes (1 displayed irreversible one electron transfer process in the cathodic region (Epc = 0.66 to 1.43 V), and nickel(II) complexes (1-4) displayed irreversible one electron oxidation process in the anodic region (Epa = 0...

The reaction of two structurally related bridging ligands bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]methane (H2L1) and bis[5-(2-pyridyl)-1,2,4-triazole-3-yl]ethane (H2L2) with copper(ii) salts resulted in a surprising wide variety of complex structures [Cu2(H2L1)Cl2]Cl2·4CH3OH (1), [Cu4(L1)4]·4H2O (2), [Cu(H2L2)(ClO4)2] (3) and [Cu3(OH)Na2(L')6](ClO4)·5H2O·C3H6O (4), where HL' is 3,5-bis-(pyridin-2-yl)-1,2,4-triazole, which were structurally characterized by the X-ray diffraction method. Complexes 1 and 2 were prepared on the H2L1 basis and have binuclear and tetranuclear structures, respectively, demonstrating strong impact of the type of counter anion on the coordination mode of the ligand...

This work demonstrates that simple copper-bipyridine compounds and atmospheric CO2 react to produce useful/complex materials under appropriate conditions. Starting from a distorted square planar copper(ii) complex, [(tbubpy)CuCl2](tbubpy = 4-tert-butyl-2-(4-tert-butylpyridin-2-yl)pyridine), an air-sensitive, copper(i) complex, [(tbubpy)2CuI][BF4], which exhibits a distorted tetrahedral geometry, was synthesized and characterized. Reactions of [(tbubpy)2CuI][BF4] with CO2 inside a sealed tube and with air were carried out over a week and three weeks, respectively...

Five new copper(II) acrylate complexes (acr is the acrylate anion: C₃H₃O₂) with imidazole derivatives (2-methylimidazole/2-MeIm, 5-methylimidazole/5-MeIm, 2-ethylimidazole/2-EtIm) of type: cis -[Cu(2-RIm)₂(acr)₂]·xH₂O (( 1 ): R = ⁻CH₃, x = 2; ( 4 ): R = ⁻CH₂⁻CH₃, x = 0), trans -[Cu(2-RIm)₂(acr)₂] (( 2 ): R = ⁻CH₃; ( 5 ): R = ⁻CH₂⁻CH₃) and trans -[Cu(5-RIm)₂(acr)₂] (( 3 ): R = ⁻CH₃) have been prepared and characterized by elemental analysis, Fourier Transform Infrared spectrometry (FTIR), Electron Paramagnetic Resonance (EPR), electronic reflectance spectroscopy, scanning electron microscopy, and mass spectrometry...

The building of robust and versatile inorganic scaffolds with artificial metallo-nuclease (AMN) activity is an important research goal for bioinorganic, biotechnology, and metallodrug research fields. Here we report a new type of AMN combining a tris-(2-pyridylmethyl)amine (TPMA) scaffold with the copper(II) N,N'-phenanthrene chemical nuclease core. In designing these complexes, we sought to employ the stabilisation and flexibility of TPMA together with the prominent chemical nuclease activity of copper 1,10-phenanthroline (Phen)...

Resins derived from natural rosin have been described recently as environmentally-friendly adsorbents with potential uses in the clean-up of wastewaters and the treatment of drinking waters. However, in order to improve the design of these products it is important to understand the chemical mechanisms through which they act. We now describe the combined use of EPR spectroscopy and Cu(II) to probe directly the metal coordination environment after uptake by various rosin-derived products. Clear distinctions are demonstrated between the copper bonding in different adsorbent preparations...

The contribution of copper complexes of salen-based Schiff bases N, N'-bis(salicylidene)ethylenediamine (C1), N, N'-bis(4-hydroxysalicylidene)ethylenediamine (C2), and N, N'-bis(5-hydroxysalicylidene)ethylenediamine (C3) to the flame retardancy of thermoplastic polyurethane (TPU) is investigated in the context of minimizing the inherent flammability of TPU. Thermal and fire properties of TPU are evaluated. It is observed that fire performances vary depending upon the substitution of the salen framework. Cone calorimetry [mass loss calorimetry (MLC)] results show that, in TPU at 10 wt % loading, C2 and C3 reduce the peak of heat release rate by 46 and 50%, respectively...

Based on the studies of the electron paramagnetic resonance parameters for two types of the Cu2+ centers in Cd(HCOO)2 ·2H2 O by using the high-order perturbation formulas for a 3d9 ion in a rhombically elongated octahedron, local structure of the doped copper ion is determined. Research suggests that the impurity Cu2+ replaces the host Cd2+ and undergoes the local rhombic elongation distortion, characterized by the axial elongation ratios of 4.1%, and 3.8% along the z-axis and the planar bond length variation ratios of 3...

Two new UiO-68 type of Zr-MOFs featuring redox non-innocent catechol-based linkers of different redox activities have been synthesized through a de novo mixed-linker strategy. Metalation of the MOFs with Cu(II) precursors triggers the reduction of Cu(II) by the phenyl-catechol groups to Cu(I) with the concomitant formation of semiquinone radicals as evidenced by EPR and XPS characterization. The MOF-supported catalysts are selective toward the allylic oxidation of cyclohexene and it is found that the presence of in situ-generated Cu(I) species exhibits enhanced catalytic activity as compared to a similar MOF with Cu(II) metalated naphthalenyl-dihydroxy groups...

Copper(II) complex of quercetin Cu+Q, mixed ligand complexes, quercetin-Cu(II)-phenanthroline [Cu+Q(PHt)] and quercetin-Cu(II)-neocuproine [Cu+Q(Neo)] have been synthesized and characterized. From the FT-IR spectroscopic studies, it was evident that C-ring of quercetin is involved in the metal chelation in all the three copper complexes. C-ring chelation was further proven by UV-Visible spectra and the presence of Cu(II) from EPR spectroscopic investigations. These complexes were found to have osteogenic and angiogenic properties, observed through in vitro osteoblast differentiation and chick embryo angiogenesis assay...

New copper(ii) complexes, [Cu(L1)2 (H2 O)](ClO4 )2 , 1 [L1 = 2-pyridin-2-yl-quinoline], [Cu(L2)2 (H2 O)](ClO4 )2 , 2 [L2 = 2-pyridin-2-yl-quinoxaline], [Cu(L3)2 (H2 O)](ClO4 )2 , 3 [L3 = 6,7-dimethyl-2-pyridin-2-yl-quinoxaline], [Cu(L4)2 (H2 O)](ClO4 )2 , 4 [L4 = 4-phenyl-2-pyridin-2-yl-quinoline] and [Cu(L5)2 (H2 O)](ClO4 )2 , 5 [L5 = 4-phenyl-2-pyridin-2-yl-quinazoline], were synthesized and characterized as catalysts for selective fixation of atmospheric CO2 . The molecular structure of 2 was determined by single-crystal X-ray studies and shown to have an unusual trigonal bipyramid geometry (τ, 0...