Poly[[tetra‐μ3‐acetato‐hexa‐μ2‐acetato‐diaqua‐μ2‐oxalato‐tetrapraseodymium(III)] dihydrate]

The title complex, {[Pr₄(C₂H₃O₂)₁₀(C₂O₄)(H₂O)₂]·2H₂O}_n, was synthesized under hydrothermal conditions from praseodymium acetate and the ionic liquid 1‐butyl‐3‐methylimidazolium chloride via an in situ oxalate‐ligand synthesis. The compound is a two‐dimensional polymer and in the structure presents tightly bound planes parallel to (100), which are in turn linked into a three‐dimensional network by hydrogen bonds involving both coordinated and solvent water molecules. The oxalate anion lies across an inversion centre and acts as a bridge between pairs of Pr atoms within a tetranuclear segment of the polymer.     

Identification of photodegradation products of Allura Red AC (E129) in a beverage by ultra high performance liquid chromatography–quadrupole-time-of-flight mass spectrometry

The study deals with the identification of the degradation products formed by simulated sunlight photoirradiation in a beverage that contains Allura Red AC (E129) dye. An UHPLC–MS/MS method that makes use of high resolution quadrupole-time-of-flight mass spectrometer, was developed. For the identification of the degradation products the software tool Information Dependent Acquisition (IDA) was used to automatically obtain information about the high resolution MS and MS/MS spectra of the species present.     

Membrane mediated regulation in free peptides of HIV-1 gp41: minimal modulation of the hemifusion phase

Membrane-mediated structural modulation in two short fragments of the human HIV-1 envelope protein gp41 is demonstrated. Derived from the C-terminal membrane proximal external (MPE) and N-terminal fusion peptide proximal (FPP) regions, these peptides are widely separated in the primary sequence but form tertiary contacts during the intermediate (hemifusion) phase of HIV infection. The structural perturbations observed at the membrane interface offer evidence of rudimentary regulatory mechanisms operating in the free peptides which may be relevant in the biological system. No such regulatory phenomena were observed for the individual peptides in a membrane environment or between the peptides in aqueous solutions. Structure determination is made using a combination of circular and linear dichroism spectroscopy (supported by calorimetric measurements) and molecular dynamics simulations. Specifically, we show that these peptides interact locally without the conformational support of helical heptad repeat regions in native gp41 and that the modulation is not mutual with the FPP peptide operating as a primary regulator of the MPE-FPP interactions in the hemifusion phase.     

New coumarin-urea based receptor for anions: a selective off–on fluorescence response to fluoride

A novel fluorosensor for anions, 1,11-bis(4-methylcoumarin-7-yl)-6-methyl-1,3,6,9,11-pentaazaundeca-2,10-dione (L), which contains two coumarin–urea units spaced by a flexible diethylenetriamine fragment, was easily prepared in 65% yield by a one-pot two-step procedure. The binding ability of L toward several anions (G) was evaluated by ¹H NMR, UV–vis, and fluorescence titration. It was found that L forms stable [LG] and [LG₂] species in both DMSO and CH₃CN solvents. Furthermore, the fluorescence emission of L in the visible range (400 nm) is affected by the presence of anions; it is quenched by acetate, chloride, and pyrophosphate while it is enhanced by fluoride. Thus, this novel fluorosensor provides a selective off–on response to the presence of fluoride in solution.     

Remote Structural Correlation in the Sequence Reactor Powder–Gel–Fiber in Polyethylenes

A series of gels originated from ultra-high-molecular-weight polyethylene reactor powders, differing in morphology due to their different synthesis prehistory, were utilized for obtaining oriented fibers through the gel technology. The source powders, gels, and drawn fibers were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and low-frequency Raman spectroscopy. A comparison of the SEM images of powders with their straight chain segment (SCS) length distributions derived from the Raman spectra showed that the samples with pronounced fibrous morphology exhibited bimodal distribution functions, whereas the granular morphological pattern was specified by the unimodal SCS length distribution. Some remnant features of the ordered structure inherent in the powders were revealed in the gels. The drawability of gel-derived fibers was found to be dependent on the SCS length distributions in the gels and, indirectly, on the morphology of the reactor powders.     

The generating graph of some monolithic groups

For a finite group G let Γ(G) denote the graph defined on the non-identity elements of G in such a way that two distinct vertices are connected by an edge if and only if they generate G. We look for conditions on the positive integer m that ensure that Γ(G) contains a Hamiltonian cycle when G=S?Cm is the wreath product of a finite simple group S and a cyclic group of order m.     

A triclinic polymorph of cyclo‐tetra‐μ‐thiosaccharinato‐κ8S:S‐tetrakis[(triphenylphosphane‐κP)silver(I)]

The triclinic structure of the title compound, cyclo‐tetrakis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato‐κ²S:S)tetrakis[(triphenylphosphane‐κP)silver(I)], [Ag₄(C₇H₄NO₂S₂)₄(C₁₈H₁₅P)₄], is a polymorph of the previously reported monoclinic structure [Dennehy, Mandolesi, Quinzani & Jennings (2007). Z. Anorg. Allg. Chem. 633 , 2746–2752]. In both polymorphs, the complex lies on a crystallographic inversion centre and the bond distances are closely comparable. Some differences can be found in the interatomic angles and torsion angles involving the inner Ag₄S₄ skeleton. The polymorphs contain essentially identical two‐dimensional layers, but with different layer stacking arrangements. In the triclinic form, all layers are related by lattice translation, while in the monoclinic form they are arranged around glide planes so that adjacent layers are mirrored with respect to each other.     

The conformations of two copper(I) complexes of 1H‐benzimidazole‐2(3H)‐thione and thiosaccharinate

(Acetonitrile‐1κN)[μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S][1H‐benzimidazole‐2(3H)‐thione‐2κS]bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₂(CH₃CN)] or [Cu₂(tsac)₂(Sbim)₂(CH₃CN)] [tsac is thiosaccharinate and Sbim is 1H‐benzimidazole‐2(3H)‐thione], (I), is a new copper(I) compound that consists of a triply bridged dinuclear Cu—Cu unit. In the complex molecule, two tsac anions and one neutral Sbim ligand bind the metals. One anion bridges via the endocyclic N and exocyclic S atoms (μ‐S:N). The other anion and one of the mercaptobenzimidazole molecules bridge the metals through their exocyclic S atoms (μ‐S:S). The second Sbim ligand coordinates in a monodentate fashion (κS) to one Cu atom, while an acetonitrile molecule coordinates to the other Cu atom. The Cu^I—Cu^I distance [2.6286 (6) Å] can be considered a strong `cuprophilic' interaction. In the case of [μ‐1H‐benzimidazole‐2(3H)‐thione‐1:2κ²S:S]bis[1H‐benzimidazole‐2(3H)‐thione]‐1κS;2κS‐bis(μ‐1,1‐dioxo‐1λ⁶,2‐benzothiazole‐3‐thiolato)‐1:2κ²S³:N;1:2κ²S³:S³‐dicopper(I)(Cu—Cu), [Cu₂(C₇H₄NO₂S₂)₂(C₇H₆N₂S)₃] or [Cu₂(tsac)₂(Sbim)₃], (II), the acetonitrile molecule is substituted by an additional Sbim ligand, which binds one Cu atom via the exocylic S atom. In this case, the Cu^I—Cu^I distance is 2.6068 (11) Å.     

Brain-like large scale cognitive networks and dynamics

A new approach to the study of the brain and its functions known as Human Connectomics has been recently established. Starting from magnetic resonance images (MRI) of brain scans, it is possible to identify the fibers that link brain areas and to build an adjacency matrix that connects these areas, thus creating the brain connectome. The topology of these networks provides a lot of information about the organizational structure of the brain (both structural and functional). Nevertheless this knowledge is rarely used to investigate the possible emerging brain dynamics linked to cognitive functions. In this work, we implement finite state models on neural networks to display the outcoming brain dynamics, using different types of networks, which correspond to diverse segmentation methods and brain atlases. From the simulations, we observe that the behavior of these systems is completely different from random and/or artificially generated networks. The emergence of stable structures, which might correspond to brain cognitive circuits, has also been detected.