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Cooper type ii epr

Prithwish Mahapatra, Soumavo Ghosh, Sanjib Giri, Vinayak Rane, Ramakant Kadam, Michael G B Drew, Ashutosh Ghosh
A new Cu(II) complex of an asymmetrically dicondensed Schiff base (H2 L = N-(2-hydroxyacetophenylidene)-N'-salicylidene-1,3-propanediamine) derived from 1,3-propanediamine, salicylaldehyde, and o-hydroxyacetophenone has been synthesized. Using this complex, [CuL] (1), as a metalloligand, two new trinuclear Cu-Mn complexes, [(CuL)2 Mn(N3 )(H2 O)](ClO4 )·H2 O (2) and [(CuL)2 Mn(NCS)2 ] (3), have been prepared. Single-crystal structural analyses reveal that complexes 2 and 3 both have the same bent trinuclear {(CuL)2 Mn}2+ structural unit in which two terminal bidentate square-planar (CuL) units are chelated to the central octahedral Mn(II) ion...
May 1, 2017: Inorganic Chemistry
Huafei Li, Yun Sun, Di Chen, He Zhao, Mengxin Zhao, Xiandi Zhu, Changhong Ke, Ge Zhang, Cheng Jiang, Li Zhang, Fulei Zhang, Huafeng Wei, Wei Li
Simultaneously blocking multiple mediators offers new hope for the treatment of complex diseases. However, the curative potential of current combination therapy by chronological administration of separate monoclonal antibodies (mAbs) or multi-specific mAbs is still moderate due to inconvenient manipulation, low cooperative effectors, poor pharmacokinetics and insufficient tumor accumulation. Here, we describe a facile strategy that arms distinct mAbs with cooperative effectors onto a long chain to form a multicomponent comb-like nano mAb...
2015: Scientific Reports
Denan Wang, Sergey V Lindeman, Adam T Fiedler
The remarkable chemistry of mononuclear complexes featuring tridentate, meridionally chelating "pincer" ligands has stimulated the development of ligand frameworks containing multiple pincer sites. Here, the coordination chemistry of a novel pentadentate ligand (L(N3O2)) that provides two closely spaced NNO pincer-type compartments fused together at a central diarylamido unit is described. The trianionic L(N3O2) chelate supports homobimetallic structures in which each M(II) ion (M = Co, Cu, Zn) is bound in a meridional fashion by the bridging diarylamido N atom and O,N-donors of the salicyaldimine arms...
September 8, 2015: Inorganic Chemistry
F Bou-Abdallah, H Yang, A Awomolo, B Cooper, M R Woodhall, S C Andrews, N D Chasteen
At least three ferritins are found in the bacterium Escherichia coli : the heme-containing bacterioferritin (EcBFR) and two nonheme bacterial ferritins (EcFtnA and EcFtnB). In addition to the conserved A and B sites of the diiron ferroxidase center, EcFtnA has a third iron-binding site (the C site) of unknown function that is nearby the diiron site. In the present work, the complex chemistry of iron oxidation and deposition in EcFtnA was further defined through a combination of oximetry, pH stat, stopped-flow and conventional kinetics, UV-vis, fluorescence, and EPR spectroscopic measurements on both the wild-type protein and site-directed variants of the A, B, and C sites...
January 28, 2014: Biochemistry
Olga Kolaj-Robin, Mohamed R Noor, Sarah R O'Kane, Frauke Baymann, Tewfik Soulimane
The Thermus thermophilus succinate:quinone reductase (SQR), serving as the respiratory complex II, has been homologously produced under the control of a constitutive promoter and subsequently purified. The detailed biochemical characterization of the resulting wild type (wt-rcII) and His-tagged (rcII-His(8)-SdhB and rcII-SdhB-His(6)) complex II variants showed the same properties as the native enzyme with respect to the subunit composition, redox cofactor content and sensitivity to the inhibitors malonate, oxaloacetate, 3-nitropropionic acid and nonyl-4-hydroxyquinoline-N-oxide (NQNO)...
2013: PloS One
Matvey V Fedin, Ksenia Yu Maryunina, Renad Z Sagdeev, Victor I Ovcharenko, Elena G Bagryanskaya
Molecular magnets Cu(hfac)(2)L(R) (hfac = hexafluoroacetylacetonate) called "breathing crystals" exhibit thermally and light-induced magnetic anomalies very similar to iron(II) spin-crossover compounds. They are physically different systems, because the spin-state switching occurs in exchange-coupled nitroxide-copper(II)-nitroxide clusters, in contrast to classical spin crossover in d(4)-d(7) transition ions. Despite this difference, numerous similarities in physical behavior of these two types of compounds have been observed, including light-induced excited spin-state trapping (LIESST) phenomenon recently found in the Cu(hfac)(2)L(R) family...
January 2, 2012: Inorganic Chemistry
Alison R Fout, Qinliang Zhao, Dianne J Xiao, Theodore A Betley
Utilizing a hexadentate ligand platform, a trinuclear manganese complex of the type ((H)L)Mn(3)(thf)(3) was synthesized and characterized ([(H)L](6-) = [MeC(CH(2)N(C(6)H(4)-o-NH))(3)](6-)). The pale-orange, formally divalent trimanganese complex rapidly reacts with O-atom transfer reagents to afford the μ(6)-oxo complex ((H)L)(2)Mn(6)(μ(6)-O)(NCMe)(4), where two trinuclear subunits bind the central O-atom and the ((H)L) ligands cooperatively bind both trinuclear subunits. The trimanganese complex ((H)L)Mn(3)(thf)(3) rapidly consumes inorganic azide ([N(3)]NBu(4)) to afford a dianionic hexanuclear nitride complex [((H)L)(2)Mn(6)(μ(6)-N)](NBu(4))(2), which subsequently can be oxidized with elemental iodine to ((H)L)(2)Mn(6)(μ(6)-N)(NCMe)(4)...
October 26, 2011: Journal of the American Chemical Society
Matvey V Fedin, Sergey L Veber, Ksenia Yu Maryunina, Galina V Romanenko, Elizaveta A Suturina, Nina P Gritsan, Renad Z Sagdeev, Victor I Ovcharenko, Elena G Bagryanskaya
Polymer-chain complexes Cu(hfac)(2)L(R) represent an interesting type of molecular magnets exhibiting thermally induced and light-induced magnetic switching, in many respects similar to a spin crossover. In the majority of these compounds the polymer chain consists of alternating one- and three-spin units composed of copper(II) ions and nitronyl nitroxides. The principal one-dimensional structure of the complexes has previously been assumed to play a key role in the observed magnetic anomalies. Using Q-band electron paramagnetic resonance (EPR) spectroscopy, we have reliably demonstrated that these complexes are indeed one-dimensional in the sense of the topology of their exchange channels; however, the magnetic chains spread across the structural polymer chains and consist solely of spin triads of nitroxide-copper(II)-nitroxide...
October 6, 2010: Journal of the American Chemical Society
Sanghamitra Mitra, Kathleen M Job, Lu Meng, Brian Bennett, Richard C Holz
An active site aspartate residue, Asp97, in the methionine aminopeptidase (MetAPs) from Escherichia coli (EcMetAP-I) was mutated to alanine, glutamate, and asparagine. Asp97 is the lone carboxylate residue bound to the crystallographically determined second metal-binding site in EcMetAP-I. These mutant EcMetAP-I enzymes have been kinetically and spectroscopically characterized. Inductively coupled plasma-atomic emission spectroscopy analysis revealed that 1.0 +/- 0.1 equivalents of cobalt were associated with each of the Asp97-mutated EcMetAP-Is...
December 2008: FEBS Journal
Debashis Adhikari, Susanne Mossin, Falguni Basuli, Benjamin R Dible, Mircea Chipara, Hongjun Fan, John C Huffman, Karsten Meyer, Daniel J Mindiola
One-electron reduction of the square-planar nickel precursor (PNP)NiCl ( 1) (PNP (-) = N[2-P(CHMe 2) 2-4-methylphenyl] 2) with KC 8 effects ligand reorganization of the pincer ligand to assemble a Ni(I) dimer, [Ni(mu 2-PNP)] 2 ( 2), containing a Ni 2N 2 core structure, as inferred by its solid-state X-ray structure. Solution magnetization measurements are consistent with a paramagnetic Ni(I) system likely undergoing a monomer <--> dimer equilibrium. The room-temperature and 4 K solid-state X-band electron paramagnetic resonance (EPR) spectra display anisotropic signals...
November 17, 2008: Inorganic Chemistry
Gaetano D Manetto, Domenico M Grasso, Danilo Milardi, Matteo Pappalardo, Rita Guzzi, Luigi Sportelli, Martin P Verbeet, Gerard W Canters, Carmelo La Rosa
The role played by the alpha-helix in determining the structure, the stability and the unfolding mechanism of azurin was addressed by studying a helix-depleted azurin variant produced by site-directed mutagenesis. The protein structure was investigated by CD, 1D (1)H NMR, fluorescence spectroscopy measurements and MD simulations, whilst EPR, UV-visible and cyclic voltammetry experiments were carried out to investigate the geometry and the properties of the Cu(II) site. The effects of the alpha-helix depletion on the thermal stability and the unfolding pathway of the protein were determined by DSC, UV/visible and fluorescence measurements at increasing temperature...
November 5, 2007: Chembiochem: a European Journal of Chemical Biology
Leonardo Marmo Moreira, Alessandra Lima Poli, Antonio José Costa-Filho, Hidetake Imasato
The equilibrium complexity involving different axially coordinated hemes is peculiar to hemoglobins. The pH dependence of the spontaneous exchange of ligands in the extracellular hemoglobin from Glossoscolex paulistus was studied using UV-Vis, EPR, and CD spectroscopies. This protein has a complex oligomeric assembly with molecular weight of 3.1 MDa that presents an important cooperative effect. A complex coexistence of different species was observed in almost all pH values, except pH 7.0, where just aquomet species is present...
October 20, 2006: Biophysical Chemistry
Laura Chiarantini, Aurora Cerasi, Luca Giorgi, Mauro Formica, Maria Francesca Ottaviani, Michela Cangiotti, Vieri Fusi
Nitric oxide is a gaseous, short-living free radical which behaves as an important signaling molecule with pleiotropic capacities including vasodilatation, neurotransmission, and microbial and tumor cell killing, as well as in tissue damage and organ-specific autoimmune disorders. Here, a synthesized, dinuclear copper complex system in vitro obtained by the simple aza-phenolic ligand 2,6-bis[[bis-(2-aminoethyl)amino]methyl]phenol (L) and Cu(II) ion has been used. The stability constants of ligand L with Cu(II) ion were determined through potentiometric measurements in aqueous solution (37...
November 2003: Bioconjugate Chemistry
Dimitri A Svistunenko, Jacqueline Dunne, Michael Fryer, Peter Nicholls, Brandon J Reeder, Michael T Wilson, Maria Giulia Bigotti, Francesca Cutruzzolà, Chris E Cooper
The reactions of hydrogen peroxide with human methemoglobin, sperm whale metmyoglobin, and horse heart metmyoglobin were studied by electron paramagnetic resonance (EPR) spectroscopy at 10 K and room temperature. The singlet EPR signal, one of the three signals seen in these systems at 10 K, is characterized by a poorly resolved, but still detectable, hyperfine structure that can be used to assign it to a tyrosyl radical. The singlet is detectable as a quintet at room temperature in methemoglobin with identical spectral features to those of the well characterized tyrosyl radical in photosystem II...
November 2002: Biophysical Journal
Y Hsieh, Y Guan, C Tu, P J Bratt, A Angerhofer, J R Lepock, M J Hickey, J A Tainer, H S Nick, D N Silverman
Structural and biochemical characterization of the nonliganding residue glutamine 143 near the manganese of human Mn superoxide dismutase (hMnSOD), a homotetramer of 22 kDa, reveals a functional role for this residue. In the wild-type protein, the side-chain amide group of Gln 143 is about 5 A from the metal and is hydrogen-bonded to Tyr 34, which is a second prominent side chain adjacent to the metal. We have prepared the site-specific mutant of hMnSOD with the conservative replacement of Gln 143 --> Asn (Q143N)...
April 7, 1998: Biochemistry
J Shen, D R Dean, W E Newton
The arginine-277 residue of the alpha-subunit of the nitrogenase MoFe protein was targeted for substitution because it is (i) a close neighbor of alpha-cysteine-275, which is one of only two residues anchoring the FeMo cofactor to the polypeptide, and (ii) a component of a potential channel for entry/exit of substrates/products and for accepting FeMo cofactor during MoFe-protein maturation. Several of the eight mutant strains constructed were capable of good diazotrophic growth and also contained FeMo cofactor as indicated by its biologically unique S = 3/2 EPR spectrum...
April 22, 1997: Biochemistry
A M Keech, N E Le Brun, M T Wilson, S C Andrews, G R Moore, A J Thomson
The iron storage protein bacterioferritin (BFR) consists of 24 identical subunits, each containing a dinuclear metal binding site called the ferroxidase center, which is essential for fast iron core formation. Cobalt(II) binding to wild-type and site-directed variants of Escherichia coli BFR was studied by optical and magnetic techniques. Data from absorption spectroscopy demonstrate the binding of two cobalt(II) ions per subunit of wild-type and heme-free BFR, each with a pseudotetrahedral or pentacoordinate geometry, and EPR studies show that the two cobalt(II) ions are weakly magnetically coupled...
January 3, 1997: Journal of Biological Chemistry
J N Herak, G Pifat, J Brnjas-Kraljević, G Jürgens
Mn(II) ions were used to study ion-binding properties of human low density lipoproteins (LDL). From the intensity of the EPR lines corresponding to the unbound Mn(II) ions the percentage of the ions bound to LDL is determined. By the titration of LDL with Mn(II) the binding parameters, dissociation constant, Kd, and the number of binding sites, n, could be derived. It has been found that there are at least two types of binding site on the LDL surface: 'strong' sites characterized by n = 6, Kd =1 x 5 x 10(-5)M x 1(-1), and 'weak' sites characterized by n = 145 and Kd = 6...
March 12, 1982: Biochimica et Biophysica Acta
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