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.     

Inverting the G‐Tetrad Polarity of a G‐Quadruplex by Using Xanthine and 8‐Oxoguanine

G‐quadruplexes are four‐stranded nucleic acid structures that are built from consecutively stacked guanine tetrad (G‐tetrad) assemblies. The simultaneous incorporation of two guanine base lesions, xanthine (X) and 8‐oxoguanine (O), within a single G‐tetrad of a G‐quadruplex was recently shown to lead to the formation of a stable G?G?X?O tetrad. Herein, a judicious introduction of X and O into a human telomeric G‐quadruplex‐forming sequence is shown to reverse the hydrogen‐bond polarity of the modified G‐tetrad while preserving the original folding topology. The control exerted over G‐tetrad polarity by joint X?O modification will be valuable for the design and programming of G‐quadruplex structures and their properties.     

The crystal and molecular structure of potassium aquapentachloroiridate(III) and the H, C, N NMR coordination shifts in iridium(III) chloride complexes with 2,2′-bipyridine or 1,10-phenanthroline

The crystal and molecular structure of potassium aquapentachloroiridate(III) (K₂[Ir(H₂O)Cl₅]) was reported. The [Ir(H₂O)Cl₅]²⁻ anions are nearly octahedral, the axial Ir–Cl bond (2.322(2) Å) being shorter than the equatorial ones (2.346(2)–2.360(2) Å); the Ir–O bond length is 2.090(4) Å. Ir(III) chloride complexes with 2,2′-bipyridine (LL = bpy) or 1,10-phenanthroline (LL = phen), of the general formulae K[Ir(LL)Cl₄] and cis-[Ir(LL)₂Cl₂]Cl, were studied by far-IR and ¹H–¹³C, ¹H–¹⁵N HMBC/HMQC/HSQC–NMR. High-frequency ¹H NMR coordination shifts (Δ^1H_coord = δ^1H_complex − δ^1H_ligand; max. ca. +1 ppm) were noted for [Ir(LL)Cl₄]⁻ anions, while for cis-[Ir(LL)₂Cl₂]⁺ cations they had variable sign and magnitude (max. ca. ±1 ppm); they were dependent on the proton position, being mostly expressed for the nitrogen-adjacent hydrogens (H(6) for bpy, H(2) for phen). ¹³C NMR signals were high-frequency shifted (by max. ca. 8 ppm), whereas all ¹⁵N nuclei were shifted to the lower frequency (by ca. 105–120 ppm). The experimental ¹H, ¹³C, ¹⁵N NMR chemical shifts were reproduced by semi-empirical quantum-chemical calculations (B3LYP/LanL2DZ+6-31G^**//B3LYP/LanL2DZ+6-31G*).     

Zinc(II) Tri‐tert‐butoxysilanethiolates. Synthesis,Properties, Crystal and Molecular Structures of [Zn{SSi(OBut)3}2(NH3)L] (L = 2‐Picoline or 2,4‐Lutidine) and [Zn{SSi(OBut)3}2(NH3)2] · MeCN Complexes

[Zn{SSi(OBu^t)₃}₂(NH₃)]₂ ( 1 ) reacts with 2‐picoline or 2,4‐lutidine (L) without elimination of ammonia giving stable monometallic complexes [Zn{SSi(OBu^t)₃}₂(NH₃)L] ( 3 and 4 ), with two different nitrogen ligands bonded to the metal center. Reaction of (Bu^tO)₃SiSH with zinc di(acetylacetonate) in ammonia atmosphere leads to the complex with two ammine ligands [Zn{SSi(OBu^t)₃}₂(NH₃)₂] · MeCN ( 5 ). Molecular and crystal structures of 3 , 4 and 5 have been determined by the single crystal X‐ray structural analysis. All have distorted tetrahedral geometry. The presence of ammonia gives rise to hydrogen bonds, different in all three cases. 3 , 4 , and 5 are the first examples of structurally characterized ammine ligated zinc thiolates.     

UV-spectroscopic study of the influence of traces of water on the protolytic equilibria of substituted pyridine N-oxides in aprotic solvents

Using a UV-spectrophotometric method, an attempt has been made to estimate quantitatively the influence of traces of water in aprotic solvents on the acidic-basic equilibria involving heterocyclic N-oxides. The N-oxides under study were pyridine N-oxide (PyO), 4-methoxy-pyridine N-oxide (4-MeOPyO), and 2-, 3-, and 4-picoline N-oxide (2-, 3-, and 4-PicO). For particular N-oxide the UV-spectra of acetonitrile solutions containing the free base and/or its simple or semiperchlorate have been recorded. To carry out the calculations various equilibrium models which include the protolytic equilibrium with water and basic species present in the solvent have been tested using the program STOICHIO which is based on non-linear regression analysis. It turned out that apart from the acidic-basic dissociation of a protonated N-oxide and cationic homoconjugation (the equilibria which are usually considered in such systems) it is absolutely necessary to take into account the protolytic equilibrium between the cationic acid and water present as impurity. Implications concerning investigations of other equilibrium systems in aprotic solvents and, in particular, the quality of the acidity constants for the calibration agents used in potentiometry are discussed.     

Modeling of the hysteresis phenomena in finite-sized slitlike nanopores. Revision of the recent results by rigorous numerical analysis

The systematic investigation of the hysteresis phenomena in finite-sized slitlike nanopores via the Aranovich-Donohue (AD) lattice density functional theory (LDFT) is presented. The new reliable quantitative modeling of the adsorption and desorption branch of the hysteresis loop, through the formation and movement of the curved meniscus, is formulated. As a result, we find that our proposal, which closely mimics the experimental findings, can reproduce a rounded shape of the desorption branch of the hysteresis loop. On the basis of the exhausted commutations, we proved that the hysteresis loop obtained in the considered finite-sized slitlike geometry is of the H1 type of the IUPAC classification. This fundamental result and the other most important results do not confirm the results of the recent studies of Sangwichien et al., whereas they fully agree with the recent lattice studies due to Monson et al. We recognize that the nature of the hysteresis loops (i.e. position, width, shape, and the multiple steps) mainly depends on the value of the energy of both the adsorbate-adsorbate and adsorbate-adsorbent interactions; however, the first one is critical for the appearance of hysteresis. Thus, for relatively small adsorbate-adsorbate interactions, the adsorption-desorption process is fully reversible in the whole region of the bulk density. We show that the strong adsorbate-adsorbent interactions produce (also observed experimentally) multiple steps within hysteresis loops. Contrary to the other studies of the hysteresis phenomena in confined geometry via the LDFT formalism, we constructed both ascending and descending scanning curves, which are known from the experimental observations. Additionally, we consider the problem of the stability of both the obtained adsorption and desorption branches of the computed hysteresis loop in finite-sized slitlike nanopores.     

Detection of Prunus Necrotic Ringspot Virus in Plant Extracts with Impedimetric Immunosensor based on Glassy Carbon Electrode

This paper concerns the development of an immunosensor for detection of Prunus necrotic ringspot virus (PNRSV) in plant extracts. The immunosensor fabrication consists of successive modification steps of glassy carbon electrodes: (i) creation of COOH groups, (ii) covalent immobilization of protein A with EDC/NHS coupling reaction, (iii) immobilization of anti‐PNRSV IgG polyclonal antibody, (iiii) filling free spaces with BSA. Each step was controlled with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The immunosensor was applied for the determination of the PNRSV virus in extracts from cucumber leaves using EIS technique. It was capable of discriminating between samples consisting of extracts from healthy plants and consisting of leaf extracts from infected plants diluted 10 000 times with extract from healthy plants.     

Improving Beamline X-ray Optics by Analyzing the Damage to Crystallographic Structure

The mission of the X-ray Characterization Laboratory in the X-ray Science Division (XSD) at the Advanced Photon Source (APS) is to support both the users and the Optics Fabrication Facility that produces high-performance optics for synchrotron X-ray beamlines. The Topography Test Unit (TTU) in the X-ray Lab has been successfully used to characterize diffracting crystals and test monochromators by quantifying residual surface stresses. This topographic method has also been adapted for testing standard X-ray mirrors, characterizing concave crystal optics and, in principle, can be used to visualize residual stresses on any optic made from single crystalline material.     

Barrelledness and bornological conditions on spaces of vector-valued μ-simple functions

Let S(μ, E) be the space of (classes of μ-a.e. equal) simple functions defined on a (non-trivial) measure space with values in a locally convex space E. The following results hold: S(μ,E) is quasi-barrelled (resp. bornological) if and only if E is quasi-barrelled (resp. bornological) and E′(β(E′,E)) has the property (B) of Pietsch; S(μ, E) is barrelled if and only if S(μ,K) is barrelled and E is barrelled and nuclear; S(μ, E) is never ultrabornological; and S(μ, E) is a DF-space if and only if E is a DF-space.