The neutral cluster amminehexa‐μ2‐chlorido‐μ4‐oxido‐tris(1,4,6‐triazabicyclo[3.3.0]oct‐4‐ene)tetracopper(II)

The title compound, [Cu₄Cl₆O(C₅H₉N₃)₃(NH₃)], is a neutral conformationally chiral cluster which crystallizes under the conditions described in this paper as a racemic conglomerate. It contains four Cu^II atoms in a tetrahedral coordination with a central O atom lying on a crystallographic threefold axis. Six chloride anions bridge the four Cu^II atoms. Three Cu^II atoms are bound by an N atom of a monodentate 1,4,6‐triazabicyclo[3.3.0]oct‐4‐ene (Htbo) ligand and the remaining Cu^II atom is bound by a terminal ammine ligand. The geometry at each copper center is trigonal bipyramidal, produced by the bound N atom of Htbo or ammonia, the O atom in the axial position, and three chloride ions in the equatorial plane. The chloride anions form an octahedron about the oxygen center. The copper–ammonia bond lies along the crystallographic threefold axis, along which the molecules are packed in a polar head‐to‐tail fashion.     

A monomeric gold(I) carbanion complex with an uncoordinated thioether: [2‐(methylsulfanyl)phenyl](triphenylphosphine)gold(I)

The title compound, [Au(C₇H₇S)(C₁₈H₁₅P)], is conformationally chiral and crystallizes from benzene–hexane as individually enantiopure crystals. This mononuclear compound has the Au^I atom linearly bound to a triphenylphosphine P atom and to a phenyl C atom of a 2‐(methylsulfanyl)phenyl group. The angle at the Au^I atom is 175.9 (2)°. The linear ligand coordination about the Au^I atom has geometric parameters inside the remarkably narrow range found for gold complexes bound by a phosphine ligand and by the ortho‐C atom of a substituted phenyl group. This is the first example of gold(I) attached to a methylsulfanyl aromatic carbanion.     

Further study of the reaction of Fe2+ with CN-: synthesis and characterization of cis and trans [FeII,III(CN)4L2]n- complexes

The reaction of Fe2+ with CN-, which was first performed in 1704, has been used to synthesize a new series of basic [FeII,III(CN)4L2]n- complexes, where L is a monodentate ligand. trans-Na2[FeII(CN)4(DMSO)2] and cis-[NEt4]2[FeII(CN)4(pyridine)2] are synthesized by the direct reaction of FeCl2 with 4 equiv of CN- in DMSO or pyridine. Air oxidation of the latter compound gives cis-[NEt4][FeIII(CN)4(pyridine)2]. The non-cyanide ligands in these complexes undergo facile ligand exchange reactions with solvent. Reaction of cis-[NEt4]2[FeII(CN)4(pyridine)2] with CO at room temperature gives trans-[NEt4]2[FeII(CN)4(pyridine)(CO)].     

Polylactic acid (PLA)/Silver-NP/VitaminE bionanocomposite electrospun nanofibers with antibacterial and antioxidant activity

The antibacterial property of silver nanoparticles (Ag-NPs) and the antioxidant activity of Vitamin E have been combined by incorporation of these two active components within polylactic acid (PLA) nanofibers via electrospinning (PLA/Ag-NP/VitaminE nanofibers). The morphological and structural characterizations of PLA/Ag-NP/VitaminE nanofibers were performed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy and X-ray diffraction. The average fiber diameter was 140 ± 60 nm, and the size of the Ag-NP was 2.7 ± 1.5 nm. PLA/Ag-NP/VitaminE nanofibers inhibited growth of Escherichia coli, Listeria monocytogenes and Salmonella typhymurium up to 100 %. The amount of released Ag ions from the nanofibers immersed in aqueous solution was determined by Inductively Coupled Plasma Mass Spectrometry, and it has been observed that the release of Ag ions was kept approximately constant after 10 days of immersion. The antioxidant activity of PLA/Ag-NP/VitaminE nanofibers was evaluated according to DPPH (2,2-diphenyl-1-picrylhydrazyl) method and determined as 94 %. The results of the tests on fresh apple and apple juice indicated that the PLA/Ag/VitaminE nanofiber membrane actively reduced the polyphenol oxidase activity. The multifunctional electrospun PLA nanofibers incorporating Ag-NP and Vitamin E may be quite applicable in food packaging due to the extremely large surface area of nanofibers along with antibacterial and antioxidant activities. These materials could find application in food industry as a potential preservative packaging for fruits and juices.     

Pressure anisotropy effects on nonlinear electrostatic excitations in magnetized electron-positron-ion plasmas

The propagation of linear and nonlinear electrostatic waves is investigated in a magnetized anisotropic electron-positron-ion (e-p-i) plasma with superthermal electrons and positrons. A two-dimensional plasma geometry is assumed. The ions are assumed to be warm and anisotropic due to an external magnetic field. The anisotropic ion pressure is defined using the double adiabatic Chew-Golberger-Low (CGL) theory. In the linear regime, two normal modes are predicted, whose characteristics are investigated parametrically, focusing on the effect of superthermality of electrons and positrons, ion pressure anisotropy, positron concentration and magnetic field strength. A Zakharov-Kuznetsov (ZK) type equation is derived for the electrostatic potential (disturbance) via a reductive perturbation method. The parametric role of superthermality, positron content, ion pressure anisotropy and magnetic field strength on the characteristics of solitary wave structures is investigated. Following Allen and Rowlands [J. Plasma Phys. 53, 63 (1995)], we have shown that the pulse soliton solution of the ZK equation is unstable to oblique perturbations, and have analytically traced the dependence of the instability growth rate on superthermality and ion pressure anisotropy.     

Posthypoxic behavioral impairment and mortality of Drosophila melanogaster are associated with high temperatures,enhanced predeath activity and oxidative stress

Hypoxia is an underlying pathophysiological condition of a variety of devastating diseases, including acute ischemic stroke (AIS). We are faced with limited therapeutic options for AIS patients, and even after successful restoration of cerebral blood flow, the poststroke mortality is still high. More basic research is needed to explain mortality after reperfusion and to develop adjunct neuroprotective therapies. Drosophila melanogaster (D.m.) is a suitable model to analyze hypoxia; however, little is known about the impacts of hypoxia and especially of the subsequent reperfusion injury on the behavior and survival of D.m. To address this knowledge gap, we subjected two wild-type D.m. strains (Canton-S and Oregon-R) to severe hypoxia (<0.3% O₂) under standardized environmental conditions in a well-constructed hypoxia chamber. During posthypoxic reperfusion (21% O₂), we assessed fly activity (evoked and spontaneous) and analyzed molecular characteristics (oxidative stress marker abundance, reactive oxygen species (ROS) production, and metabolic activity) at various timepoints during reperfusion. First, we established standard conditions to induce hypoxia in D.m. to guarantee stable and reproducible experiments. Exposure to severe hypoxia under defined conditions impaired the climbing ability and reduced the overall activity of both D.m. strains. Furthermore, a majority of the flies died during the early reperfusion phase (up to 24 h). Interestingly, the flies that died early exhibited elevated activity before death compared to that of the flies that survived the entire reperfusion period. Additionally, we detected increases in ROS and stress marker (Catalase, Superoxide Dismutase and Heat Shock Protein 70) levels as well as reductions in metabolic activity in the reperfusion phase. Finally, we found that changes in environmental conditions impacted the mortality rate. In particular, decreasing the temperature during hypoxia or the reperfusion phase displayed a protective effect. In conclusion, our data suggest that reperfusion-dependent death might be associated with elevated temperatures, predeath activity, and oxidative stress.Subject terms: Stroke, Molecular neuroscience     

Local structure in perovskite relaxor ferroelectrics: high-resolution Nb 3QMAS NMR

Solid solutions of (1'-x)Pb(Mg(1/3)Nb(2/3))O3xPb(Sc(1/2)Nb(1/2))O3 (PMN/PSN) have been investigated using high-resolution 93Nb 3-quantum magic-angle spinning nuclear magnetic resonance experiments (3QMAS NMR). In previous MAS NMR investigations, the local B-cation ordering in these relaxor ferroelectric solid solutions was quantitatively determined. However, in conventional one-dimensional MAS spectra the effects of chemical shifts and quadrupole interaction are convoluted; this, in addition to the insufficient resolution, precludes reliable extraction of the values of isotropic chemical shift and quadrupole coupling product. In the current 3QMAS investigation, 93Nb spectra are presented for concentrations x=0, 0.1, 0.2, 0.6, 0.7, and 0.9 at high magnetic field (19.6 T) and fast sample spinning speed (35.7 kHz). Seven narrow peaks and two broad components are observed. The unique high-resolution of the two-dimensional 3QMAS spectra enables unambiguous and consistent assignments of spectral intensities to the specific 28 nearest B-site neighbor (nBn) configurations, (NMg, NSc, NNb) where each number ranges from 0 to 6 and their sum is 6. It is now possible to isolate the isotropic chemical shift and quadrupole coupling product and separately determine their values for most of the 28 nBn configurations. The isotropic chemical shift depends linearly on the number of Mg2+ cations in the configuration; delta iso CS=(13.7 +/- 0.1)NMg-970 +/- 0.4 ppm, regardless of the ratio NSc/NNb. For the seven Nb5+-deficient configurations (NMg, 6-NMg, 0) and the pure niobium configuration (0, 0, 6), the quadrupole coupling products (and hence the electric field gradients) are small (PQ approximately 6-12 MHz) and for the remaining configurations containing small, ferroelectric active Nb5+ ions, the quadrupole coupling products are significantly larger (PQ approximately 40 MHz), indicating larger electric field gradients.     

Phenomenon observed at the onset of micellization using static light scattering

A phenomenon was observed near the critical micelle concentration (cmc) of surfactants using static light scattering. This consists of an unexpected peak in light scattering as the concentration varies between zero and above the cmc. This work studied three different surfactants: the two ionic surfactants hexadecyltrimethylammonium bromide (CTABr) and sodium dodecyl sulfate (SDS) and the nonionic surfactant Triton X-100. Peaks were observed for all three under different conditions such as varying ionic strengths and different concentration paths. These peaks are real, are reproducible, and appear to have static properties.     

Tetranuclear, Oxygen Centered Copper(II) Clusters Linked Together with Guanidine-Guanidinate Ligands

The reaction of copper(I) chloride with Htbo (1,4,6-triazabicyclo[3.3.0]oct-4-ene) under reflux in THF with oxidation by oxygen, produces a neutral cluster comprising two oxo-tetra-copper(II) units connected by six tbo⁻ bridges three of them bind two and the other three bind four metals; each unit also contains three chlorine bridges and a Htbo terminal ligand. Two different X-ray crystal structures (1a, 1b) have been determined and the magnetic behavior has been studied. The molar magnetic susceptibility measurements indicate strong exchange interactions within an oxo cluster with coupling constants of J ₁ = −163 cm⁻¹ and J ₂ = −1.1 cm⁻¹, and a weak interaction across the guanidinate bridges of J ₃ = −5.2 cm⁻¹ of the octa-Cu^II cluster.