A Novel Human TGF-β1 Fusion Protein in Combination with rhBMP-2 Increases Chondro-Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

Transforming growth factor-beta (TGF-β) is involved in processes related to the differentiation and maturation of osteoprogenitor cells into osteoblasts. Rat bone marrow (BM) cells were cultured in a collagen-gel containing 0.5% fetal bovine serum (FBS) for 10 days in the presence of rhTGF (recombinant human TGF)-β1-F2, a fusion protein engineered to include a high-affinity collagen-binding decapeptide derived from von Willebrand factor. Subsequently, cells were moderately expanded in medium with 10% FBS for 4 days and treated with a short pulse of rhBMP (recombinant human bone morphogenetic protein)-2 for 4 h. During the last 2 days, dexamethasone and β-glycerophosphate were added to potentiate osteoinduction. Concomitant with an up-regulation of cell proliferation, DNA synthesis levels were determined. Polymerase chain reaction was performed to reveal the possible stemness of these cells. Osteogenic differentiation was evaluated in terms of alkaline phosphatase activity and mineralized matrix formation as well as by mRNA expression of osteogenic marker genes. Moreover, cells were placed inside diffusion chambers and implanted subcutaneously into the backs of adult rats for 4 weeks. Histological study provided evidence of cartilage and bone-like tissue formation. This experimental procedure is capable of selecting cell populations from BM that, in the presence of rhTGF-β1-F2 and rhBMP-2, achieve skeletogenic potential in vitro and in vivo.     

Mangiferin Reduces the Inhibition of Chondrogenic Differentiation by IL-1β in Mesenchymal Stem Cells from Subchondral Bone and Targets Multiple Aspects of the Smad and SOX9 Pathways

Mangiferin is a natural immunomodulator found in plants including mango trees. The effects of mangiferin on chondrogenesis and cartilage repair have not yet been reported. This study was designed to determine the effect of mangiferin on chondrogenic differentiation in IL-1β-stimulated mesenchymal stem cells (MSCs) from subchondral bone and to explore the mechanisms underlying these effects. MSCs were isolated from the subchondral bone of rabbit and treated with mangiferin alone and/or interleukin-1β (IL-1β). Mangiferin induced chondrogenic differentiation in MSCs by upregulating transforming growth factor (TGF)-β, bone morphogenetic protein (BMP)-2, and BMP-4 and several key markers of chondrogenesis, including sex-determining region Y–box (SRY-box) containing gene 9 (SOX9), type 2α1 collagen (Col2α1), cartilage link protein, and aggrecan. In IL-1β-stimulated MSCs, mangiferin significantly reversed the production of TGF-β, BMP-2, BMP-4, SOX9, Col2α1, cartilage link protein, and aggrecan, as well as matrix metalloproteinase (MMP)-1, MMP-13, and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS5). Mangiferin upregulated the phosphorylation of Smad 2, Smad 3, Smad 1/5/8, and SOX9 in IL-1β-stimulated MSCs. In the presence of mangiferin, SOX9 siRNA suppressed the activation of Smad 2, Smad 3, Smad 1/5/8, aggrecan, and Col2α1 expression. In conclusion, mangiferin exhibits both chondrogenic and chondroprotective effects on damaged MSCs and mediates these effects by targeting multiple aspects of the Smad and SOX9 signaling pathways.     

Mesenchymal Stem Cells Preserve Working Memory in the 3xTg-AD Mouse Model of Alzheimer’s Disease

The transplantation of stem cells may have a therapeutic effect on the pathogenesis and progression of neurodegenerative disorders. In the present study, we transplanted human mesenchymal stem cells (MSCs) into the lateral ventricle of a triple transgenic mouse model of Alzheimer´s disease (3xTg-AD) at the age of eight months. We evaluated spatial reference and working memory after MSC treatment and the possible underlying mechanisms, such as the influence of transplanted MSCs on neurogenesis in the subventricular zone (SVZ) and the expression levels of a 56 kDa oligomer of amyloid β (Aβ*56), glutamine synthetase (GS) and glutamate transporters (Glutamate aspartate transporter (GLAST) and Glutamate transporter-1 (GLT-1)) in the entorhinal and prefrontal cortices and the hippocampus. At 14 months of age we observed the preservation of working memory in MSC-treated 3xTg-AD mice, suggesting that such preservation might be due to the protective effect of MSCs on GS levels and the considerable downregulation of Aβ*56 levels in the entorhinal cortex. These changes were observed six months after transplantation, accompanied by clusters of proliferating cells in the SVZ. Since the grafted cells did not survive for the whole experimental period, it is likely that the observed effects could have been transiently more pronounced at earlier time points than at six months after cell application.     

Hypoxic Conditioned Medium from Human Amniotic Fluid-Derived Mesenchymal Stem Cells Accelerates Skin Wound Healing through TGF-β/SMAD2 and PI3K/Akt Pathways

In a previous study, we isolated human amniotic fluid (AF)-derived mesenchymal stem cells (AF-MSCs) and utilized normoxic conditioned medium (AF-MSC-norCM) which has been shown to accelerate cutaneous wound healing. Because hypoxia enhances the wound healing function of mesenchymal stem cell-conditioned medium (MSC-CM), it is interesting to explore the mechanism responsible for the enhancement of wound healing function. In this work, hypoxia not only increased the proliferation of AF-MSCs but also maintained their constitutive characteristics (surface marker expression and differentiation potentials). Notably, more paracrine factors, VEGF and TGF-β1, were secreted into hypoxic conditioned medium from AF-MSCs (AF-MSC-hypoCM) compared to AF-MSC-norCM. Moreover, AF-MSC-hypoCM enhanced the proliferation and migration of human dermal fibroblasts in vitro, and wound closure in a skin injury model, as compared to AF-MSC-norCM. However, the enhancement of migration of fibroblasts accelerated by AF-MSC-hypoCM was inhibited by SB505124 and {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002, inhibitors of TGF-β/SMAD2 and PI3K/AKT, suggesting that AF-MSC-hypoCM-enhanced wound healing is mediated by the activation of TGF-β/SMAD2 and PI3K/AKT. Therefore, AF-MSC-hypoCM enhances wound healing through the increase of hypoxia-induced paracrine factors via activation of TGF-β/SMAD2 and PI3K/AKT pathways.     

Shikonin Inhibits the Migration and Invasion of Human Glioblastoma Cells by Targeting Phosphorylated β-Catenin and Phosphorylated PI3K/Akt: A Potential Mechanism for the Anti-Glioma Efficacy of a Traditional Chinese Herbal Medicine

Shikonin is an anthraquinone derivative extracted from the root of lithospermum. Shikonin is traditionally used in the treatment of inflammatory and infectious diseases such as hepatitis. Shikonin also inhibits proliferation and induces apoptosis in various tumors. However, the effect of shikonin on gliomas has not been fully elucidated. In the present study, we aimed to investigate the effects of shikonin on the migration and invasion of human glioblastoma cells as well as the underlying mechanisms. U87 and U251 human glioblastoma cells were treated with shikonin at 2.5, 5, and 7.5 μmol/L and cell viability, migration and invasiveness were assessed with CCK8, scratch wound healing, in vitro Transwell migration, and invasion assays. The expression and activity of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) and the expression of phosphorylated β-catenin (p-β-catenin) and phosphorylated PI3K/Akt were also checked. Results showed that shikonin significantly inhibited the cell proliferation, migration, invasion, and expression of MMP-2 and MMP-9 in U87 and U251 cells. The expression of p-β-catenin showed contrary trends in two cell lines. It was significantly inhibited in U87 cells and promoted in U251 cells. Results in this work indicated that shikonin displayed an inhibitory effect on the migration and invasion of glioma cells by inhibiting the expression and activity of MMP-2 and -9. In addition, shikonin also inhibited the expression of p-PI3K and p-Akt to attenuate cell migration and invasion and MMP-2 and MMP-9 expression in both cell lines, which could be reversed by the PI3K/Akt pathway agonist, insulin-like growth factor-1 (IGF-1).     

Expression of IL-8, IL-6 and IL-1β in Tears as a Main Characteristic of the Immune Response in Human Microbial Keratitis

Corneal infections are frequent and potentially vision-threatening diseases, and despite the significance of the immunological response in animal models of microbial keratitis (MK), it remains unclear in humans. The aim of this study was to describe the cytokine profile of tears in patients with MK. Characteristics of ocular lesions such as size of the epithelial defect, stromal infiltration, and hypopyon were analyzed. Immunological evaluation included determination of interleukine (IL)-1β, IL-6, IL-8, IL-10, IL-12 and tumor necrosis factor (TNF)-α in tear samples obtained from infected eyes of 28 patients with MK and compared with their contralateral non-infected eyes. Additionally, frequency of CD4⁺, CD8⁺, CD19⁺ and CD3⁻CD56⁺ cells was also determined in peripheral blood mononuclear cells in patients with MK, and compared with 48 healthy controls. Non-significant differences were observed in the size of the epithelial defect, stromal infiltration, and hypopyon. Nevertheless, we found an immunological profile apparently related to MK etiology. IL-8 > IL-6 in patients with bacterial keratitis; IL-8 > IL-6 > IL-1β and increased frequency of circulating CD3⁻CD56⁺ NK cells in patients with gram-negative keratitis; and IL-8 = IL-6 > IL-1β in patients with fungal keratitis. Characterization of tear cytokines from patients with MK could aid our understanding of the immune pathophysiological mechanisms underlying corneal damage in humans.     

Reaction of the titanocene alkyne complex Cp2Ti(η2-Me3SiC2SiMe3) with selenium dioxide: Preparation and characterization of a novel tetranuclear titanium complex with selenium and oxo bridges

The low valent titanocene(II) source Cp₂Ti(η²-Me₃SiC₂SiMe₃) 1 reacts with selenium dioxide (2) to obtain a tetranuclear selenium and oxygen bridged titanocene(IV) [{Cp₂Ti(µ²-O; µ²-Se)CpTi}₂(µ²-O)] 6. The molecular structure was confirmed by X-ray analysis.     

Insight into the strengthening mechanism of α-Al2O3/γ-Fe ceramic-metal interface doped with Cr,Ni, Mg,and Ti

Corrosion prevention is an important issue in thermal energy storage. The poor bonding strength between the ceramic coatings and substrates in these energy storage devices arises because of the high corrosivity of the energy storage materials at high temperatures, which reduces the service life of the devices. In this study, an alloy element x (Cr, Ni, Mg, or Ti) was innovatively doped into the α-Al₂O₃ (0001)/γ-Fe (111) interface to enhance the interfacial bonding strength, and the strengthening mechanism of the doped interface was quantitatively analysed by first-principles calculations at the electronic level. The results show that Ti and Mg doping can clearly increase the bonding strength of the Al₂O₃/Fe interface, whereas doping with Ni and Cr is ineffective. More importantly, the micro-mechanism was revealed by discussing the segregation behaviour, where the Ti and Mg dopants readily segregated to the interface and then combined with Al or O atoms to form new compounds (Ti₂O₃, TiAl₂, MgO, and MgAl₃), whereas the Cr and Ni dopants were preferentially and stably localized in the Fe sites. Therefore, Mg and Ti atoms appear to play the enhancement effect as interfacial binders. Furthermore, evaluation of the electronic structure confirmed that all doped interfaces exhibited metallic and covalent characteristics at the interfaces, whereas greater hybridisation of the electron orbitals was found at the doped Ti and Mg interfaces than at the other interfaces, such as between Al-s and Mg-p, between Al-p and Mg-p, between Ti-p and Al-p, between Ti-s and Al-s, and between Ti-p, d and O-s. The more electron orbitals hybridizing, the larger the bonding strength is.     

DAG/PKCδ and IP3/Ca2+/CaMK IIβ Operate in Parallel to Each Other in PLCγ1-Driven Cell Proliferation and Migration of Human Gastric Adenocarcinoma Cells,through Akt/mTOR/S6 Pathway

Phosphoinositide specific phospholipase Cγ (PLCγ) activates diacylglycerol (DAG)/protein kinase C (PKC) and inositol 1,4,5-trisphosphate (IP3)/Ca²⁺/calmodulin-dependent protein kinase II (CaMK II) axes to regulate import events in some cancer cells, including gastric adenocarcinoma cells. However, whether DAG/PKCδ and IP3/Ca²⁺/CaMK IIβ axes are simultaneously involved in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells and the underlying mechanism are not elucidated. Here, we investigated the role of DAG/PKCδ or CaMK IIβ in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells, using the BGC-823 cell line. The results indicated that the inhibition of PKCδ and CaMK IIβ could block cell proliferation and migration of BGC-823 cells as well as the effect of inhibiting PLCγ1, including the decrease of cell viability, the increase of apoptotic index, the down-regulation of matrix metalloproteinase (MMP) 9 expression level, and the decrease of cell migration rate. Both DAG/PKCδ and CaMK IIβ triggered protein kinase B (Akt)/mammalian target of rapamycin (mTOR)/S6 pathway to regulate protein synthesis. The data indicate that DAG/PKCδ and IP3/Ca²⁺/CaMK IIβ operate in parallel to each other in PLCγ1-driven cell proliferation and migration of human gastric adenocarcinoma cells through Akt/mTOR/S6 pathway, with important implication for validating PLCγ1 as a molecular biomarker in early gastric cancer diagnosis and disease surveillance.     

Effects of B2O3 and P2O5 doping on the microstructure evolution and mechanical strength in a lithium aluminosilicate glass–ceramic material with TiO2 and ZrO2

During the devitrification process, the coordination number of Ti changes from 4 and 5 to 6; and the coordination number of Zr changes from 6 to 8 in a lithium aluminosilicate glass–ceramic material. The flexural strength of the glass–ceramics strongly depends on the composition of additives. The strength of a well-crystallized sample increases 45% by doping with B₂O₃ and decreases 56% by doping with P₂O₅. Thermal expansion mismatch and microstructure non-uniformity are the proposed mechanisms responsible for the changes in strength. The effects of doping concentration of B₂O₃ and P₂O₅ and thermal treatment conditions on the microstructure and mechanical strength of a lithium aluminosilicate glass–ceramic material with TiO₂ and ZrO₂ were studied. The local environment around Ti and Zr correlated to the secondary phase development, such as TiZrO₄ and ZrSiO₄, during the crystallization process was observed by X-ray absorption near edge structure. The electronic structure of each peak in the X-ray absorption near edge spectra was also assigned in terms of phase evolutions. The phase transformation temperature of β-quartz solid solutions to β-spodumene solid solutions is decreased for about 100 °C by adding B₂O₃ and P₂O₅.     

Na(+), K(+)-ATPase Subunit Composition in a Human Chondrocyte Cell Line; Evidence for the Presence of α1, α3, β1, β2 and β3 Isoforms

Membrane transport systems participate in fundamental activities such as cell cycle control, proliferation, survival, volume regulation, pH maintenance and regulation of extracellular matrix synthesis. Multiple isoforms of Na(+), K(+)-ATPase are expressed in primary chondrocytes. Some of these isoforms have previously been reported to be expressed exclusively in electrically excitable cells (i.e., cardiomyocytes and neurons). Studying the distribution of Na(+), K(+)-ATPase isoforms in chondrocytes makes it possible to document the diversity of isozyme pairing and to clarify issues concerning Na(+), K(+)-ATPase isoform abundance and the physiological relevance of their expression. In this study, we investigated the expression of Na(+), K(+)-ATPase in a human chondrocyte cell line (C-20/A4) using a combination of immunological and biochemical techniques. A panel of well-characterized antibodies revealed abundant expression of the α1, β1 and β2 isoforms. Western blot analysis of plasma membranes confirmed the above findings. Na(+), K(+)-ATPase consists of multiple isozyme variants that endow chondrocytes with additional homeostatic control capabilities. In terms of Na(+), K(+)-ATPase expression, the C-20/A4 cell line is phenotypically similar to primary and in situ chondrocytes. However, unlike freshly isolated chondrocytes, C-20/A4 cells are an easily accessible and convenient in vitro model for the study of Na(+), K(+)-ATPase expression and regulation in chondrocytes.     

How to Attain Ultralow Interfacial Tension and Three-Phase Behavior with a Surfactant Formulation for Enhanced Oil Recovery: a Review—Part 3. Practical Procedures to Optimize the Laboratory Research According to the Current State of the Art in Surfactant Mixing

The minimum interfacial tension to be reached in enhanced oil recovery by surfactant flooding implies the attainment of a so-called optimum formulation. Part 1 of the present review showed that this formulation may be described as a numerical correlation between the involved variables defining the oil, the water, the surfactant and the temperature. Since it is unlikely to find a single surfactant matching the crude/brine/T/P system characteristic of a reservoir, a mixture of at least two surfactant species is always used. The scan technique method to test the mixing requires about ten interfacial tension or phase behavior experiments and results in a single data. Hence, the scan experiments have to be repeated many times to find a minimum tension which is low enough, e.g. 0.001 mN/m, for the given crude oil-brine system. Part 2 of this review has shown that there are many formulation variables and thus too many possibilities to easily choose experimental conditions. Since there is no simple method to select two or more surfactant species, the choice is made from partial experience or intuition, and sometimes at random. The laboratory time and cost to reach an appropriate optimum formulation is often excessive. Part 3 of this review shows that by cleverly using a three-surfactant mixture, the experimental work to attain a very low interfacial tension for a given reservoir case can be considerably reduced. It is a matter of using the available information along a proper sequential step by step path toward the optimum.     

Dicyanamido–metal(II) complexes. Part 3: Hydrolysis of the dicyanamide into amidocyanamide during its interaction with Cu(II) perchlorate and 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine

The reaction of Cu(ClO₄)₂, 2-pyridylcarbonyl-N,N-bis(2-pyridylmethyl)amine (DPA-CO-py) and sodium dicyanamide (Nadca) in aqueous medium led to the isolation of three complexes: {[Cu(DPA)(μ_1,5-dca)]ClO₄}_n (1), [Cu₂(pic)₂(μ_1,3-H₂NCO–N–CN)₂(H₂O)₂] · 2H₂O (2) and Cu(pic)₂ · H₂O (3). The Cu²⁺ ion, during its complex formation with DPA-CO-py and dca not only assisted the hydrolysis of DPA-CO-py to the corresponding di(2-methylpyridyl)amine (DPA) and picolinic acid (Hpic) but also resulted in partial hydrolysis of one of the two nitrile groups of the dicyanamide, NC–N–CN^? (dca) to amidocynamide, H₂NCO–NH–CN. The complexes were structurally characterized and the single X-ray structures for 1 and 2 reveal their identity. Complex 1 forms a 1D polymeric chain with the dca acting as a μ_1,5-bridging ligand via the terminal nitrile nitrogen atoms. A distorted SP geometry around the Cu²⁺ centers was achieved by the three N-atoms of the DPA and by the two nitrile groups of the bridging dca ligands. Complex 2 consists of a dimeric unit with CuN₃O₂ chromophore in coordination polyhedron that has a distorted SP geometry. The amidocyanamide ion, H₂NCO–N–CN^? acts as bis(monodentate) μ_1,3-bridging ligand via the central amido and terminal nitrile nitrogen atoms whereas the picolinate anion forms a six-membered chelate ring through its pyridyl nitrogen and an oxygen atom of the carboxylate group, and the aqua water occupies the apical position of the structure. Complex 1 exhibits very weak antiferromagnetic coupling (J = ?0.31 cm^?1) whereas 2 shows a significant antiferromagnetic interaction between the two copper centers (J = ?13.6 cm^?1).     

Two new selenidostannates with a [Sn3Se7]n2n− layer from the imidazolium-based ionic liquids: The role of (Bzmim)+ and aggregated cation of [(Emim)3Cl]2+

Herein, we report on the syntheses, crystal structures, and optical properties of two new selenidostannates, namely, [Emim]₅[Sn₃Se₇]₂Cl (1, Emim = 1-ethyl-3-methylimidazolium) and [Bzmim]₂[Sn₃Se₇] (2, Bzmim = 1-benzyl-3-methylimidazolium). The ionic liquids (ILs) of [Emim]Cl with a short ethyl chain and [Bzmim]Cl with a bulky substituent benzyl group were used in the syntheses of compounds 1 and 2, respectively. Although both the structures feature an anionic lamellar [Sn₃Se₇]_n^2n– layer, the packing of the layers are dramatically different; such structural diversity may be ascribed to the difference of structure-directing cations incorporated in between the layers, that is [(Emim)₃Cl]²⁺ aggregates in 1 and bulky [Bzmim]⁺ in 2, respectively.     

Studies on the synthesis of cholane derivatives containing a mercapto group and their dimers with disulfide spacers. Part 2. 3α-Mercapto-5β-cholane-7α,12α,24-triol and its C(3)–C(3′) disulfide dimer

Two new sulfur-containing cholane derivatives were obtained from cholic acid: 3α-mercapto-5β-cholane-7α,12α,24-triol 2 and its C(3)–C(3′) disulfide dimer 3 as a potential supramolecular host.     

Synthesis and Study of Isomorphous Miscibility Limits of Crystalline Phases with a Hollandite-Type Tunnel Structure in the Cs2O(MeO)–Al2O3–TiO2 (Me = Ba, Sr) Systems*

The possibility of forming hollandite-type phases during the solid-phase reaction in the Cs₂O(MeO)–Al₂O₃–TiO₂ (Me = Ba, Sr) systems is studied. It is revealed that, in the Cs₂O–BaO–Al₂O₃–TiO₂ system, the region of existence of Cs _x Ba_{1 – x/2}Al₂Ti₅O₁₄ solid solutions with a hollandite-type structure lies in the concentration range 0 x 0.7. In the SrO–BaO–Al₂O₃–TiO₂ system, no solid solutions with a hollandite-type structure are observed. The mechanism and kinetics of formation of the Cs _x Ba_{1 – x/2}Al₂Ti₅O₁₄ (0 x 0.7) solid solutions are analyzed, and the optimum conditions for synthesis of these solutions are determined.     

The evidence of phase separation droplets in the crystallization process of a Li2O-Al2O3-SiO2 glass with TiO2 as nucleating agent – An X-ray diffraction and (S)TEM-study supported by EDX-analysis

Lithiumalumosilicate glasses are of great importance for industrial applications, because they enable the preparation of glass ceramics with coefficients of thermal expansion close to zero. While detailed studies of the effect of ZrO₂ on nucleation and crystal growth have already been performed in recent years, the effect of TiO₂ was up to now not reported in detail. It is shown for the first time, that liquid/liquid phase separation is the initial step of nucleation in lithiumalumosilicate glasses containing TiO₂. During temperature treatment above the glass transition temperature, at 740 °C for 0.25–24 h, in the formed droplets, TiO₂ nanocrystals precipitate. The formed phases were investigated by XRD- and TEM and STEM-EDX to illustrate the phase developments as well as the resulting microstructures and the local enrichments of the respective components as a function of time.Longer crystallization times resulted in the formation of crystalline lithiumalumosilicate (LAS) with a high-quartz structure. These crystals are notably larger than the TiO₂ crystals and are growing with increasing treatment time and temperature. The evidence of anatase formation was obtained from high resolution TEM from the lattice spacings because it cannot be distinguished from the high quartz structure using XRD.     

Inhibiting HDS and HYD reactions with quinoline on Co(Ni)–PMo(W)/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts: Effect of active phase composition on stability in the hydrotreatment of a model petroleum raw material

Со(Ni)–PMo(W)/Al₂O₃ catalysts are prepared using Keggin heteropoly acids H₃PMo(W)₁₂O₄₀ and cobalt (nickel) citrate. The physicochemical properties of the catalysts are studied via low-temperature nitrogen adsorption, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy. Their catalytic properties are determined in the hydrotreatment of a model raw material containing dibenzothiophene, naphthalene, and different amounts of quinoline (up to 1000 ppm of nitrogen), and in the hydrotreatment of a straight-run diesel fraction and vacuum gas oil. The composition of Со(Ni)–PMo(W)/Al₂O₃ catalysts plays an important role in the hydrotreatment of a complex hydrocarbon raw material. Ni–PW/Al₂O₃ catalyst is more resistant to organonitrogen inhibitors than Ni(Co)–PMo/Al₂O₃ samples with more reactive active sites. Ni–PW/Al₂O₃ catalyst provides the greatest depth of conversion for sulfur- and nitrogen-containing compounds and polycyclic aromatic hydrocarbons in the hydrotreatment of vacuum gas oil.     

The redox pair {(μ4-TCNE)[Fe(CO)2(C5H5)]4}4+/3+: Surprisingly small metal–ligand interaction and the first resolved EPR hyperfine structure (13C, 14N, 57Fe) of a tetranuclear complex with TCNE−

Electrochemistry and absorption spectroscopy (UV/Vis, IR) of the complex {(μ₄-TCNE)[Fe(CO)₂(C₅H₅)]₄}(BF₄)₄ reveal only a small degree of metal-to-ligand π back donation, in contrast to previously characterized compounds [(TCNE)(ML_n)₄]. Accordingly, the one-electron reduced {(μ₄-TCNE)[Fe(CO)₂(C₅H₅)]₄}³⁺ exhibits a very well resolved EPR spectrum at g = 1.9965 with detectable coupling of 0.055 mT for ⁵⁷Fe in natural abundance from four coordinated [Fe(CO)₂(C₅H₅)]⁺ groups.