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Cooper EPR

Thomas Simler, Sylvie Choua, Andreas A Danopoulos, Pierre Braunstein
The double aminolysis reaction of [Co{N(SiMe3)2}2] by the salt 1-(6-((dicyclohexylphosphaneyl)methyl)pyridin-2-yl)-3-(2,6-diisopropylphenyl)-1H-imidazol-3-ium bromide, which contains one phosphane, one pyridine and one imidazolium groups, of formula [o-Cy2PCH2(C5H3N)(o-C3H3N2DiPP)]Br and abbreviated as (CyPNpyrCim)Br, was previously shown to afford the Co(ii) complex [Co(CyP*NaCNHC)Br] (1) containing a dearomatised picolyl moiety in the tridentate, anionic donor ligand CyP*NaCNHC (Na = anionic amido, P* = vinylic P donor)...
May 18, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
A Giannoulis, K Ackermann, P E Spindler, C Higgins, D B Cordes, A M Z Slawin, T F Prisner, B E Bode
Fundamentally, the stability of coordination complexes and of templated (bio)macromolecular assemblies depends on the thermodynamic and kinetic properties of the intermediates and final complexes formed. Here, we used pulse EPR (electron paramagnetic resonance) spectroscopy to determine the stabilities of nanoscopic assemblies formed between one or two nitroxide spin-labelled tridentate 2,2':6',2''-terpyridine (tpy) ligands and divalent metal ions (FeII, ZnII, CoII and CuII). In three distinct approaches we exploited (a) the modulation depth of pulsed electron-electron double resonance (PELDOR) experiments in samples with increasing metal-to-ligand ratios, (b) the frequencies of PELDOR under broadband excitation using shaped pulses and (c) the distances recovered from well-resolved PELDOR data in fully deuterated solvents measured at 34 GHz...
April 25, 2018: Physical Chemistry Chemical Physics: PCCP
Julie Kengen, Jean-Philippe Deglasse, Marie-Aline Neveu, Lionel Mignion, Céline Desmet, Florian Gourgue, Jean-Christophe Jonas, Bernard Gallez, Bénédicte F Jordan
The ability of certain cancer cells to maintain a highly reduced intracellular environment is correlated with aggressiveness and drug resistance. Since the glutathione (GSH) and thioredoxin (TRX) systems cooperate to a tight regulation of ROS in cell physiology, and to a stimulation of tumour initiation and progression, modulation of the GSH and TRX pathways are emerging as new potential targets in cancer. In vivo methods to assess changes in tumour redox status are critically needed to assess the relevance of redox-targeted agents...
February 2018: Free Radical Research
José A Amaya, Cooper D Rutland, Nicholas Leschinsky, Thomas M Makris
Cytochrome P450 OleT utilizes hydrogen peroxide (H2 O2 ) to catalyze the decarboxylation or hydroxylation of fatty acid (FA) substrates. Both reactions are initiated through the abstraction of a substrate hydrogen atom by the high-valent iron-oxo intermediate known as Compound I. Here, we specifically probe the influence of substrate coordination on OleT reaction partitioning through the combined use of fluorescent and electron paramagnetic resonance (EPR)-active FA probes and mutagenesis of a structurally disordered F-G loop that is distal from the heme-iron active site...
January 23, 2018: Biochemistry
Alexander V Polezhaev, Cameron J Liss, Joshua Telser, Chun-Hsing Chen, Kenneth G Caulton
Reaction of the unsymmetrically armed pincer PNNH (phosphine-pyridyl-pyrazole) ligand with FeCl2 yielded the five-coordinate monomer [(PNNH)FeCl2 ], the NH proton of which captures THF through the formation of a hydrogen bond. Deprotonation of this NH functionality with Li[N(SiMe3 )2 ] did not give the four-coordinate [(PNN)FeCl], but instead retained LiCl to yield [(PNNLi)FeCl2 ], in which the lithium bridges between the pyrazolate β-nitrogen and one of the chlorides on iron. One-electron reduction of this compound under CO occurred with the loss of LiCl to form the square-pyramidal monovalent iron in [(PNN)Fe(CO)2 ], which was characterized by IR, Mössbauer, and EPR spectroscopy, X-ray diffraction, and DFT calculations...
January 26, 2018: Chemistry: a European Journal
J-R Jiménez, M Tricoire, D Garnier, L-M Chamoreau, J von Bardeleben, Yves Journaux, Yanling Li, R Lescouëzec
We report a new cyanide-bridged Cs⊂{Fe4 Co4 } box, a soluble model of photomagnetic Prussian blue analogues (PBAs). The Cs+ ion has a high affinity for the box and can replace the K+ ion in the preformed K-cube. This exchange is kinetically impeded at room temperature but is accelerated by heating and using the 18-crown-6 ether. The inserted Cs+ ion confers a high robustness to the cube, which withstands boiling, as shown by variable-temperature NMR studies. The stability of this model complex in solution allows the probing of the electronic interaction between the alkali ion and the cyanide cage by using various techniques...
November 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Arnab Mandal, Sanchari Dasgupta, Sumi Ganguly, Antonio Bauzá, Antonio Frontera, Debasis Das
Four cobalt(iii) complexes, [Co(HL1 )(NCS)2 (EtOH)] (1), [Co2 (L1 )2 (N3 )2 ] (2) and [Co(HL2 )(NCS)2 (EtOH)] (3), [Co(HL2 )(N3 )2 ] (4) were synthesized from two Schiff-base ligands namely, (E)-2-((2-(2-hydroxyethylamino)ethylimino)methyl)phenol (H2L1) and (E)-2-((3-(2-hydroxyethylamino)propylimino)methyl)phenol (H2L2), respectively. All the four complexes have been thoroughly characterised by using various physicochemical studies such as UV-Vis, FT-IR, ESI-MS, EPR and single crystal X-ray diffraction. Depending on flexibility of the ligand backbone subtle structural differences are observed in the synthesized complexes...
November 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Arun Khajuria, Jonathon Ward, George Cooper, Jonathon Stevenson, Michael Parry, Lee Jeys
INTRODUCTION: Patients with failed hip arthroplasty requiring extensive femoral reconstruction often present with a multitude of comorbidities. Many treatment options limit initial mobilisation relying on bone graft incorporation. The use of endoprosthetic replacement (EPR), despite often being a "last resort", offers an expeditious solution with early mobilisation that is crucial in the comorbid individual. Many perceive that the surgical insult of EPR is associated with an increased mortality...
January 2018: Hip International: the Journal of Clinical and Experimental Research on Hip Pathology and Therapy
Jacqueline R Ward, Kommireddy Vasu, Emily Deutschman, Dalia Halawani, Peter A Larson, Dongmei Zhang, Belinda Willard, Paul L Fox, John V Moran, Michelle S Longworth
LINE-1 (L1) retrotransposons can mobilize (retrotranspose) within the human genome, and mutagenic de novo L1 insertions can lead to human diseases, including cancers. As a result, cells are actively engaged in preventing L1 retrotransposition. This work reveals that the human Condensin II complex restricts L1 retrotransposition in both non-transformed and transformed cell lines through inhibition of L1 transcription and translation. Condensin II subunits, CAP-D3 and CAP-H2, interact with members of the Gamma-Interferon Activated Inhibitor of Translation (GAIT) complex including the glutamyl-prolyl-tRNA synthetase (EPRS), the ribosomal protein L13a, Glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and NS1 associated protein 1 (NSAP1)...
October 2017: PLoS Genetics
Olive J Njuma, Ian Davis, Elizabeth N Ndontsa, Jessica R Krewall, Aimin Liu, Douglas C Goodwin
KatG is a bifunctional, heme-dependent enzyme in the front-line defense of numerous bacterial and fungal pathogens against H2 O2 -induced oxidative damage from host immune responses. Contrary to the expectation that catalase and peroxidase activities should be mutually antagonistic, peroxidatic electron donors (PxEDs) enhance KatG catalase activity. Here, we establish the mechanism of synergistic cooperation between these activities. We show that at low pH values KatG can fully convert H2 O2 to O2 and H2 O only if a PxED is present in the reaction mixture...
November 10, 2017: Journal of Biological Chemistry
Abideen Idowu Adeogun, Sarafadeen Olateju Kareeem, Oluwatobi Samson Adebayo, Saka Adebayo Balogun
The role of enzyme engineering in biotechnology, biological and pharmaceutical process cannot be over emphasized. This study compared the adsorption of digestives enzymes; amylase, protease and lipase on to Zn-ferrite (ZnFe2 O4 ). The metal ferrite was synthesized via a sol-gel technique and characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), Electron paramagnetic resonance (EPR) and Fourier transform infrared spectroscopy (FTIR). The adsorption was studied in a batch process and the data were subjected to kinetics and isotherm models...
July 2017: 3 Biotech
Jian-Hua Zhang, Jia-Jun Xia, Jonathan M Garibaldi, Petros P Groumpos, Ru-Bin Wang
BACKGROUND AND OBJECTIVE: In human-machine (HM) hybrid control systems, human operator and machine cooperate to achieve the control objectives. To enhance the overall HM system performance, the discrete manual control task-load by the operator must be dynamically allocated in accordance with continuous-time fluctuation of psychophysiological functional status of the operator, so-called operator functional state (OFS). The behavior of the HM system is hybrid in nature due to the co-existence of discrete task-load (control) variable and continuous operator performance (system output) variable...
June 2017: Computer Methods and Programs in Biomedicine
Jonathan Cremers, Sabine Richert, Dmitry V Kondratuk, Tim D W Claridge, Christiane R Timmel, Harry L Anderson
The affinity of copper(ii) porphyrins for pyridine ligands is extremely weak, but oligo-pyridine templates can be used to direct the synthesis of Cu-containing cyclic porphyrin oligomers when they also have Zn centers. We report the synthesis of two heterometallated nanorings: a six-porphyrin ring prepared from a Zn/Cu/Zn linear trimer and a ten-porphyrin ring prepared from a Zn/Zn/Cu/Zn/Zn pentamer. Both these macrocycles have copper porphyrins at two specific positions across the diameter of the ring and zinc at other sites...
December 1, 2016: Chemical Science
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
Elena Smolensky Koganov, Gregory Leitus, Rinat Rozin, Lev Weiner, Noga Friedman, Mordechai Sheves
Xanthorhodopsin (xR) is a member of the retinal protein family and acts as a proton pump in the cell membranes of the extremely halophilic eubacterium Salinibacter ruber. In addition to the retinal chromophore, xR contains a carotenoid, which acts as a light-harvesting antenna as it transfers 40% of the quanta it absorbs to the retinal. Our previous studies have shown that the CD and absorption spectra of xR are dramatically affected due to the protonation of two different residues. It is still unclear whether xR can bind cations...
May 4, 2017: Journal of Physical Chemistry. B
Andreas Schlundt, Jan-Niklas Tants, Michael Sattler
Recent advances in RNA sequencing technologies have greatly expanded our knowledge of the RNA landscape in cells, often with spatiotemporal resolution. These techniques identified many new (often non-coding) RNA molecules. Large-scale studies have also discovered novel RNA binding proteins (RBPs), which exhibit single or multiple RNA binding domains (RBDs) for recognition of specific sequence or structured motifs in RNA. Starting from these large-scale approaches it is crucial to unravel the molecular principles of protein-RNA recognition in ribonucleoprotein complexes (RNPs) to understand the underlying mechanisms of gene regulation...
April 15, 2017: Methods: a Companion to Methods in Enzymology
Tao Deng, Yanan Peng, Rong Zhang, Jie Wang, Jie Zhang, Yueqing Gu, Dechun Huang, Dawei Deng
Exploring the organic-to-aqueous phase transfer of quantum dots (QDs) is significant for achieving their versatile applications in biomedical fields. In this thematic issue, surface modification, size control, and biocompatibility of QDs and QDs-based nanocomposites are core problems. Herein, the new highly fluorescent tumor-targeted QDs-clusters consisting of ZnAgInSe/ZnS (ZAISe/ZnS) QDs and sulfobetaine-PIMA-histamine (SPH) polymer with the ανβ3 integrin receptor cyclic RGD (c-RGD) were developed via ligand exchange and an accompanying self-assembly process...
March 23, 2017: ACS Applied Materials & Interfaces
Marianna Marchini, Massimo Baroncini, Giacomo Bergamini, Paola Ceroni, Mila D'Angelantonio, Paola Franchi, Marco Lucarini, Fabrizia Negri, Tomasz Szreder, Margherita Venturi
A shape-persistent molecule, featuring four bipyridinium units, has been synthesized that upon reduction undergoes intermolecular pimerization because of the rigid architecture of the molecule. The pimerization process has been investigated by a variety of techniques, such as absorption measurements, EPR spectroscopy, as well as gamma and pulse radiolysis, and compared with the behavior of a model compound. Computational studies have also been performed to support the experimental data. The most interesting feature of the tetramer is that pimerization occurs only above a threshold concentration of monoreduced species, on the contrary to the model compound...
May 5, 2017: Chemistry: a European Journal
Margarethe van der Meer, Yvonne Rechkemmer, Uta Frank, Frauke D Breitgoff, Stephan Hohloch, Cheng-Yong Su, Petr Neugebauer, Raphael Marx, María Dörfel, Joris van Slageren, Biprajit Sarkar
Quinonoid ligands are excellent bridges for generating redox-rich dinuclear assemblies. A large majority of these bridges are symmetrically substituted, with examples of unsymmetrically substituted quinonoid bridges being extremely rare. We present here a dicobalt complex in its various redox states with an unsymmetrically substituted quinonoid bridging ligand. Two homovalent forms and one mixed-valent form have been isolated and characterized by single crystal X-ray diffraction. The complex displays a large comproportionation constant for the mixed-valent state which is three orders of magnitude higher than that observed for the analogous complex with a symmetrically substituted bridge...
September 19, 2016: Chemistry: a European Journal
Feng-Chun Lo, Chang-Chih Hsieh, Manuel Maestre-Reyna, Chin-Yu Chen, Tzu-Ping Ko, Yih-Chern Horng, Yei-Chen Lai, Yun-Wei Chiang, Chih-Mao Chou, Cheng-Hung Chiang, Wei-Ning Huang, Yi-Hung Lin, D Scott Bohle, Wen-Feng Liaw
Molecular mechanisms underlying the repair of nitrosylated [Fe-S] clusters by the microbial protein YtfE remain poorly understood. The X-ray crystal structure of YtfE, in combination with EPR, magnetic circular dichroism (MCD), UV, and (17) O-labeling electron spin echo envelope modulation measurements, show that each iron of the oxo-bridged Fe(II) -Fe(III) diiron core is coordinatively unsaturated with each iron bound to two bridging carboxylates and two terminal histidines in addition to an oxo-bridge. Structural analysis reveals that there are two solvent-accessible tunnels, both of which converge to the diiron center and are critical for capturing substrates...
July 4, 2016: Chemistry: a European Journal
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