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https://www.readbyqxmd.com/read/29105162/a-pnnh-pincer-ligand-allows-access-to-monovalent-iron
#1
Alexander V Polezhaev, Cameron J Liss, Joshua Telser, Chun-Hsing Chen, Kenneth G Caulton
Reaction of the unsymmetrically-armed pincer PNNH (phosphine, pyridyl, pyrazole) with FeCl2 yields a five coordinate monomer (PNNH)FeCl2, whose NH proton hydrogen bonds to capture THF. Deprotonation of this NH functionality with Li[N(SiMe3)2] does not give four coordinate (PNN)FeCl, but instead retains LiCl to yield (PNNLi)FeCl2, where Li bridges between the pyrazolate beta nitrogen and one chloride on Fe. One electron reduction of this compound under CO occurs with loss of LiCl to form square pyramidal monovalent iron in (PNN)Fe(CO)2, which is characterized by IR, Mössbauer, X-ray diffraction, EPR measurements and DFT calculations...
November 3, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29091087/a-new-fe4co4-soluble-switchable-nanomagnet-encapsulating-cs-enhancing-the-stability-and-redox-flexibility-and-tuning-the-photomagnetic-effect
#2
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⊂{Fe4Co4} 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
https://www.readbyqxmd.com/read/29068013/cooperative-influence-of-pseudohalides-and-ligand-backbone-of-schiff-bases-on-nuclearity-and-stereochemistry-of-cobalt-iii-complexes-experimental-and-theoretical-investigation
#3
Arnab Mandal, Sanchari Dasgupta, Sumi Ganguly, Antonio Bauzá, Antonio Frontera, Debasis Das
Four cobalt(iii) complexes, [Co(HL(1))(NCS)2(EtOH)] (1), [Co2(L(1))2(N3)2] (2) and [Co(HL(2))(NCS)2(EtOH)] (3), [Co(HL(2))(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
https://www.readbyqxmd.com/read/29048688/is-endoprosthetic-replacement-of-the-proximal-femur-appropriate-in-the-comorbid-patient
#4
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...
October 16, 2017: Hip International: the Journal of Clinical and Experimental Research on Hip Pathology and Therapy
https://www.readbyqxmd.com/read/29028794/condensin-ii-and-gait-complexes-cooperate-to-restrict-line-1-retrotransposition-in-epithelial-cells
#5
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
https://www.readbyqxmd.com/read/28972181/mutual-synergy-between-catalase-and-peroxidase-activities-of-the-bifunctional-enzyme-katg-is-facilitated-by-electron-hole-hopping-within-the-enzyme
#6
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 H2O2-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 H2O2 to O2 and H2O only if a PxED is present in the reaction mixture...
November 10, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28667640/comparative-adsorption-of-amylase-protease-and-lipase-on-znfe2o4-kinetics-isothermal-and-thermodynamics-studies
#7
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 (ZnFe2O4). 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
https://www.readbyqxmd.com/read/28494999/modeling-and-control-of-operator-functional-state-in-a-unified-framework-of-fuzzy-inference-petri-nets
#8
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
https://www.readbyqxmd.com/read/28451130/nanorings-with-copper-ii-and-zinc-ii-centers-forcing-copper-porphyrins-to-bind-axial-ligands-in-heterometallated-oligomers
#9
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
https://www.readbyqxmd.com/read/28387507/subtle-structural-changes-in-cu-ii-l-2mn-ii-complexes-to-induce-heterometallic-cooperative-catalytic-oxidase-activities-on-phenolic-substrates-h2l-salen-type-unsymmetrical-schiff-base
#10
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 (H2L = 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)2Mn(N3)(H2O)](ClO4)·H2O (2) and [(CuL)2Mn(NCS)2] (3), have been prepared. Single-crystal structural analyses reveal that complexes 2 and 3 both have the same bent trinuclear {(CuL)2Mn}(2+) structural unit in which two terminal bidentate square-planar (CuL) units are chelated to the central octahedral Mn(II) ion...
April 7, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28379004/cation-binding-to-xanthorhodopsin-electron-paramagnetic-resonance-and-magnetic-studies
#11
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
https://www.readbyqxmd.com/read/28315749/integrated-structural-biology-to-unravel-molecular-mechanisms-of-protein-rna-recognition
#12
REVIEW
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...
March 16, 2017: Methods: a Companion to Methods in Enzymology
https://www.readbyqxmd.com/read/28293947/water-solubilizing-hydrophobic-znaginse-zns-qds-with-tumor-targeted-crgd-sulfobetaine-pima-histamine-ligands-via-a-self-assembly-strategy-for-bioimaging
#13
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
https://www.readbyqxmd.com/read/28263437/hierarchical-growth-of-supramolecular-structures-driven-by-pimerization-of-tetrahedrally-arranged-bipyridinium-units
#14
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...
March 6, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/27549247/a-dicobalt-complex-with-an-unsymmetrical-quinonoid-bridge-isolated-in-three-units-of-charge-a-combined-structural-spectro-electrochemical-magnetic-and-spectroscopic-study
#15
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
https://www.readbyqxmd.com/read/27246459/crystal-structure-analysis-of-the-repair-of-iron-centers-protein-ytfe-and-its-interaction-with-no
#16
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
https://www.readbyqxmd.com/read/27207587/the-h-bond-network-surrounding-the-pyranopterins-modulates-redox-cooperativity-in-the-molybdenum-bispgd-cofactor-in-arsenite-oxidase
#17
Simon Duval, Joanne M Santini, David Lemaire, Florence Chaspoul, Michael J Russell, Stephane Grimaldi, Wolfgang Nitschke, Barbara Schoepp-Cothenet
While the molybdenum cofactor in the majority of bisPGD enzymes goes through two consecutive 1-electron redox transitions, previous protein-film voltammetric results indicated the possibility of cooperative (n=2) redox behavior in the bioenergetic enzyme arsenite oxidase (Aio). Combining equilibrium redox titrations, optical and EPR spectroscopies on concentrated samples obtained via heterologous expression, we unambiguously confirm this claim and quantify Aio's redox cooperativity. The stability constant, Ks, of the Mo(V) semi-reduced intermediate is found to be lower than 10(-3)...
September 2016: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/27192943/exceptional-photosensitivity-of-a-polyoxometalate-based-charge-transfer-hybrid-material
#18
Jian-Zhen Liao, Chen Wu, Xiao-Yuan Wu, Shui-Quan Deng, Can-Zhong Lu
An unusual room-temperature light sensitivity was realized in a polyoxometalate-based hybrid material due to cooperative multicomponent molecular charge-transfer interactions taking place in this material, mainly among POMs, NDIs, and other molecules. The functional π-acidic NDI linkers and POM clusters in the discussed hybrid material were individually designed as photosensors and electron reservoirs. To propose a photo-induced charge-transfer mechanism, EPR, XPS, UV-Vis and computational studies were carried out, and indicated the presence of active charge-transfer interactions among several of the components...
May 31, 2016: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/27138102/divergent-assembly-mechanisms-of-the-manganese-iron-cofactors-in-r2lox-and-r2c-proteins
#19
Yuri Kutin, Vivek Srinivas, Matthieu Fritz, Ramona Kositzki, Hannah S Shafaat, James Birrell, Eckhard Bill, Michael Haumann, Wolfgang Lubitz, Martin Högbom, Julia J Griese, Nicholas Cox
A manganese/iron cofactor which performs multi-electron oxidative chemistry is found in two classes of ferritin-like proteins, the small subunit (R2) of class Ic ribonucleotide reductase (R2c) and the R2-like ligand-binding oxidase (R2lox). It is unclear how a heterodimeric Mn/Fe metallocofactor is assembled in these two related proteins as opposed to a homodimeric Fe/Fe cofactor, especially considering the structural similarity and proximity of the two metal-binding sites in both protein scaffolds and the similar first coordination sphere ligand preferences of Mn(II) and Fe(II)...
September 2016: Journal of Inorganic Biochemistry
https://www.readbyqxmd.com/read/27104767/cyanide-scavenging-by-a-cobalt-schiff-base-macrocycle-a-cost-effective-alternative-to-corrinoids
#20
Elisenda Lopez-Manzano, Andrea A Cronican, Kristin L Frawley, Jim Peterson, Linda L Pearce
The complex of cobalt(II) with the ligand 2,12-dimethyl-3,7,11,17-tetraazabicyclo-[11.3.1]heptadeca-1(17)2,11,13,15-pentaene (CoN4[11.3.1]) has been shown to bind two molecules of cyanide in a cooperative fashion with an association constant of 2.7 (±0.2) × 10(5). In vivo, irrespective of whether it is initially administered as the Co(II) or Co(III) cation, EPR spectroscopic measurements on blood samples show that at physiological levels of reductant (principally ascorbate) CoN4[11.3.1] becomes quantitatively reduced to the Co(II) form...
June 20, 2016: Chemical Research in Toxicology
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