Development of chiral N,N-ditopic metalloligands based on a Cinchona alkaloids' backbone for constructing homochiral coordination polymers

The bimetallic chiral bipyridyl-type metalloligands based on aluminium derivatives of cinchonine, [R(2)Al(μ-CN)](2) (R = Me or Et), in combination with the corresponding ZnR(2) compound as nodes were used for the generation of novel homochiral heterometallic coordination polymers of either zig-zag or helical topology, depending on the character of the R substituent.     

tert-Butylzinc hydroxide as an efficient predesigned precursor of ZnO nanoparticles

The reaction of (t)Bu(2)Zn with water was investigated which led to isolation of the novel hexameric tert-butylzinc hydroxide. The resulting zinc hydroxide cluster appears to be an ideal predesigned single-source precursor which decomposes smoothly in one step at only ca. 120 °C into ZnO nanoparticles.     

Electrochemical and Biological Studies on Reactivity of [VO(oda)(H2O)2], [Co(oda)(H2O)2]·H2O,and [Ni(oda)­(H2O)3]·1.5H2O Towards Superoxide Free Radicals

The reactivity of superoxide free radicals (O₂ ^{· –}) generated electrochemically towards the oxydiacetate metal complexes, namely [VO(oda)(H₂O)₂], [Co(oda)(H₂O)₂] · H₂O, and [Ni(oda)(H₂O)₃] · 1.5H₂O (oda = oxydiacetate) was examined by cyclic voltammetry. The measurements were carried out in DMSO solution using a platinum electrode. Based on the height of the anodic peak E_a that corresponds to electrochemical oxidation O₂ ^{· –} → O₂ + e, in the absence and in the presence of the compounds in the mixture, their O₂ ^{· –} scavenge ability was assessed. The influence of the type of the complex was briefly discussed. H₂O₂ was used to induce cellular injury in a mouse hippocampal cell line (HT22). The cytoprotection of chemical compounds was tested at the mitochondrial (MTT test) and plasma membrane level (LDH leakage). Dose‐dependent effect (10 and 100 μM of the complex) of investigated compounds was observed.     

Redox Active Dipyrromethene?Cu(II) Monolayer for Oriented Immobilization of His‐Tagged RAGE Domains – the Base of Electrochemical Biosensor for Determination of Aβ16–23′

The new system which consists of the thiol derivative of dipyrromethene–Cu(II) complex created on the surface of a gold electrode was applied for the first time for oriented immobilization of selected His‐tagged domains of a receptor for advanced glycation endproducts (RAGE). Cyclic voltammetry (CV), Osteryoung square‐wave voltammetry (OSWV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) were used for characterization of the redox active sensing layer. The biosensor proposed was applied for determination of Aβ_16–23′ peptide. In its presence, a decrease of the maximum Cu(II) redox current was observed. These values correlated linearly with the Aβ_16–23′ concentration in the range 0.001–1.000 µM. The presence of diluted human plasma has no influence on the sensor responses.     

A novel convergent synthesis of the potent antiglaucoma agent travoprost

The 16-(3-trifluoromethyl)phenoxy PGF_2α analogue travoprost (8a) has potent topical ocular activity. A novel convergent synthesis of 13,14-en-15-ol PGF_2α analogues was developed employing Julia–Lythgoe olefination of the structurally advanced prostaglandin phenylsulfone (5Z)-(+)-15 with a new enantiomerically pure aldehyde ω-chain synthon (S)-(?)-16a. Subsequent hydrolysis of protecting groups and final esterification of fluprostenol (7a) yielded travoprost (8a). The main advantages are the preparation of high purity travoprost (8a) and the application of comparatively cheap reagents. The novel convergent strategy allows the synthesis of a whole series of 13,14-en-15-ol PGF_2α analogues from a common and structurally advanced prostaglandin intermediate 15. The preparation and identification of two synthetic impurities, 15-epi isomer (8b) of travoprost and a new prostaglandin related ester (5Z)-(+)-18, are also described.     

Macrocyclic multicenter complexes of nickel and copper of increasing complexity

Multicenter (bi-, tri-, and tetranuclear) tetraazamacrocyclic complexes were self-assembled from Ni and Cu tetraazamacrocyclic mononuclear units and α,ω-diamines as building blocks. The structures of all compounds studied were proved by spectroscopic methods (ESI MS and NMR spectroscopy). Electrochemical experiments revealed reversible one-electron electrode processes at each of the Ni(2+) and Cu(2+) centers with formation of metal cations in oxidation state +3. Long linkers allow bi- and trinuclear complexes with noninteracting metal centers to be obtained. In the case of the short linkers (e.g. ethylenediamine) higher, trinuclear species are formed as major product. The structures of the bis- and tris-macrocyclic systems were confirmed by single-crystal X-ray diffraction. The tris-macrocyclic systems form cations in the shape of triangles partially filled with counterions and solvent molecules. The cations form positively charged layers, which interact in the crystal lattice with the neighboring negatively charged layers of anions. In solution, the trinuclear complexes exhibit strong host-guest interactions with 9,10-dimethyltriptycene due to complementarity of shape and size of this guest molecule. The association constants were determined by NMR spectroscopy and voltammetry, and very good agreement was obtained. The structural flexibility of the tetranuclear complex with long linkers allows for attractive interactions between the metal-complexing macrocycles that result in folding of the molecule. On the contrary, no folding is possible in the case of short linkers consisting of two CH(2) groups.     

Application of the finite segment method to stabilisation of the force in a riser connection with a wellhead

This paper presents a spatial model of riser dynamics formulated using the segment method and its applications. The model has been validated by comparison of the authors’ own results with those obtained from experimental measurements and Abaqus on the basis of forced vibration with large amplitude for the riser submerged in water. The influence of the sea environment is considered. Correctness and numerical effectiveness of the model enable us to formulate and solve the force stabilisation problem. A dynamic optimisation problem is formulated and solved. As a result vertical courses of movement of the upper end of the riser are obtained which compensate the horizontal movement of the base and stabilise the force in the connection of the riser with a wellhead.     

Chemical Components of Oxytropis pseudoglandulosa Induce Apoptotic-Type Cell Death of Caco-2 Cells

Oxytropis pseudoglandulosa plant is used in traditional Mongolian medicine. However, its chemical composition and biological properties are poorly explored. In this study, the total content of polyphenols and flavonoids as well as antioxidant activity were verified in plant extract. The total phenolic and flavonoid contents were determined by spectrometric (6.62 mg GAE/g and 10.32 mg QE/g) and chromatographic (17,598 mg/kg and 17,467 mg/kg) assays. The antioxidant potential was investigated by DPPH assay and yielded IC₅₀ at 18.76 µg/mL. Twelve phenolic compounds were identified as components of O. pseudoglandulosa extract. Kaempferol-3-O-robinosyl-7-O-rhamnoside and kaempferol-3-(p-coumaroyl)-rutinosyl-7-rhamnoside made up 80% of determined components and were found to be the major polyphenolic compounds. The biological properties of O. pseudoglandulosa extracts were determined in vitro using human epithelial adenocarcinoma Caco-2 cell line. Low concentrations of extract (0–30 µg/mL) exhibited protective effects against cell damage caused by chemically induced oxidative stress. Elevated concentrations, on the other hand, resulted in apoptotic-type cell death induction. Metabolic failure, ROS elevation and membrane permeabilization observed in cells upon incubation with extract dosages above 50 µg/mL allowed us to conclude on O. pseudoglandulosa being predominantly a necrosis inducer.     

Synthesis of Four Enantiomers of (1-Amino-3-Hydroxypropane-1,3-Diyl)Diphosphonic Acid as Diphosphonate Analogues of 4-Hydroxyglutamic Acid

All the enantiomers of (1-amino-3-hydroxypropane-1,3-diyl)diphosphonic acid, newly design phosphonate analogues of 4-hydroxyglutamic acids, were obtained. The synthetic strategy involved Abramov reactions of diethyl (R)- and (S)-1-(N-Boc-amino)-3-oxopropylphosphonates with diethyl phosphite, separation of diastereoisomeric [1-(N-Boc-amino)-3-hydroxypropane-1,3-diyl]diphosphonates as O-protected esters, followed by their hydrolysis to the enantiomeric phosphonic acids. The absolute configuration of the enantiomeric phosphonates was established by comparing the ³¹P NMR chemical shifts of respective (S)-O-methylmandelic acid esters obtained from respective pairs of syn- and anti-[1-(N-Boc-amino)-3-hydroxypropane-1,3-diyl]diphosphonates according to the Spilling rule.     

CO2 Adsorption Study of Potassium-Based Activation of Carbon Spheres

The adsorption properties of microporous spherical carbon materials obtained from the resorcinol-formaldehyde resin, treated in a solvothermal reactor heated with microwaves and then subjected to carbonization, are presented. The potassium-based activation of carbon spheres was carried out in two ways: solution-based and solid-based methods. The effect of various factors, such as chemical agent selection, chemical activating agent content, and the temperature or time of activation, was investigated. The influence of microwave treatment on the adsorption properties was also investigated and described. The adsorption performance of carbon spheres was evaluated in detail by examining CO₂ adsorption from the gas phase.