Systematic Study of the Interaction Between VIV Centres and LnIII Ions in Well Defined {V 2 IV LnIII}{AsIIIW9O33}2 Sandwich-Type Clusters: Part 2

The gadolinium (Gd) member of a new type of heteropolytungstates that contain one lanthanide and two transition metal ions in a triangular arrangement is reported. The compound NaK₆Gd_0.33 [((VO)₂Gd(H₂O)₄K₂(H₂O)₂(Na)(H₂O)₂)(α-B-AsW₉O₃₃)₂]·24H₂O (1) was prepared from acidified aqueous solutions of Na₂WO₄·2H₂O, As₂O₃ and VOSO₄·5H₂O to which Gd³⁺ ions were added. The single crystal X-ray structure analysis (monoclinic, space group P2₁/m) shows that the anion consists of two [α-B-As^IIIW₉O₃₃]^9? trilacunary Keggin-type units linked by two VO²⁺, one Gd³⁺ as well as weakly by two K⁺ and one Na⁺ ions, resulting in a sandwich-type structure with idealized C _2v symmetry. The problem of positioning crystal lattice and special polyoxometalate sites with different cations is discussed also in connection with supramolecular chemistry aspects and as an option for further research. A fit of the magnetic susceptibility yielded exchange coupling constants of J _VV = ?2.55 cm^?1 (anti-ferromagnetic) between the vanadium ions and J _GdV = 0.6 cm^?1 (ferromagnetic) between the Gd and each of the two vanadium ions. The complete magnetochemical analysis also revealed a partial occupancy of the Na⁺ sites in the counter-cation–water system by Gd³⁺ ions (0.33 Gd³⁺ ions in total).     

Offline and online capillary electrophoresis enzyme assays of β-N-acetylhexosaminidase

Enzyme assays of β-N-acetylhexosaminidase from Aspergillus oryzae using capillary electrophoresis in the offline and online setup have been developed. The pH value and concentration of the borate-based background electrolyte were optimized in order to achieve baseline separation of N,N′,N″-triacetylchitotriose, N,N′-diacetylchitobiose, and N-acetyl-d-glucosamine. The optimized method using 25 mM tetraborate buffer, pH 10.0, was evaluated in terms of repeatability, limits of detection, quantification, and linearity. The method was successfully applied to the offline enzyme assay of β-N-acetylhexosaminidase, which was demonstrated by monitoring the hydrolysis of N,N′,N″-triacetylchitotriose. The presented method was also utilized to study the pH dependence of enzyme activity. An online assay with N,N′-diacetylchitobiose as a substrate was developed using the Transverse Diffusion of Laminar Flow Profiles model to optimize the injection sequence and in-capillary mixing of substrate and enzyme plugs. The experimental results were in good agreement with predictions of the model. The online assay was successfully used to observe the inhibition effect of N,N′-dimethylformamide on the activity of β-N-acetylhexosaminidase with nanoliter volumes of reagents used per run and a high degree of automation. After adjustment of background electrolyte pH, an online assay with N,N′,N″-triacetylchitotriose as a substrate was also performed.

The preparation of the 239Np tracer from 243Am and the purification of the stock solution

The present work describes preparation of ²³⁹Np tracer from ²⁴³Am stock solution and the purification of this solution from ferric cation. The method of the preparation of tracer involves stabilization of Np(IV) by ascorbic acid and ferric nitrate, separation of ²³⁹Np from ²⁴³Am by extraction chromatography and determination of recoveries of ²³⁹Np by means of gamma spectroscopy. We used the commercially available sorbents TEVA^®Resin for the ²³⁹Np preparation and DGA Resin for ²⁴³Am purification. All sorbents were purchased from Eichrom Industries, Inc. The first eluate from the column can be stored for a future preparation of the tracer and fraction with ²³⁹Np will be used to monitor radiochemical yield of ²³⁷Np.     

The Family of Ferrocene‐Stabilized Silylium Ions: Synthesis, 29Si NMR Characterization,Lewis Acidity,Substituent Scrambling,and Quantum‐Chemical Analyses

The purpose of this systematic experimental and theoretical study is to deeply understand the unique bonding situation in ferrocene‐stabilized silylium ions as a function of the substituents at the silicon atom and to learn about the structure parameters that determine the ²⁹Si NMR chemical shift and electrophilicity of these strong Lewis acids. For this, ten new members of the family of ferrocene‐stabilized silicon cations were prepared by a hydride abstraction reaction from silanes with the trityl cation and characterized by multinuclear ¹H and ²⁹Si NMR spectroscopy. A closer look at the NMR spectra revealed that additional minor sets of signals were not impurities but silylium ions with substitution patterns different from that of the initially formed cation. Careful assignment of these signals furnished experimental proof that sterically less hindered silylium ions are capable of exchanging substituents with unreacted silane precursors. Density functional theory calculations provided mechanistic insight into that substituent transfer in which the migrating group is exchanged between two silicon fragments in a concerted process involving a ferrocene‐bridged intermediate. Moreover, the quantum‐chemical analysis of the ²⁹Si NMR chemical shifts revealed a linear relationship between δ(²⁹Si) values and the Fe???Si distance for subsets of silicon cations. An electron localization function and electron localizability indicator analysis shows a three‐center two‐electron bonding attractor between the iron, silicon, and C′_ipso atoms, clearly distinguishing the silicon cations from the corresponding carbenium ions and boranes. Correlations between ²⁹Si NMR chemical shifts and Lewis acidity, evaluated in terms of fluoride ion affinities, are seen only for subsets of silylium ions, sometimes with non‐intuitive trends, indicating a complicated interplay of steric and electronic effects on the degree of the Fe???Si interaction.     

Monitoring of amoxicilline and ceftazidime in the microdialysate of diabetic foot and serum by capillary electrophoresis with contactless conductivity detection

Determination of the broad-spectrum antibiotics amoxicilline (AMX) and ceftazidime (CTZ) in blood serum and microdialysates of the subcutaneous tissue of the lower limbs is performed using CE with contactless conductivity detection (C⁴D). Baseline separation of AMX is achieved in 0.5 M acetic acid as the background electrolyte and separation of CTZ in 3.2 M acetic acid with addition of 13% v/v methanol. The CE-C⁴D determination is performed in a 25 µm capillary with suppression of the EOF using INST-coating on an effective length of 18 cm and the attained migration time is 4.2 min for AMX and 4.4 min for CTZ. The analysis was performed using 20 µl of serum and 15 µl of microdialysate, treated by the addition of acetonitrile in a ratio of 1/3 v/v and the sample is injected into the capillary using the large volume sample stacking technique. The LOQ attained in the microdialysate is 148 ng/ml for AMX and 339 ng/ml for CTZ, and in serum 143 ng/ml for AMX and 318 ng/ml for CTZ. The CE-C⁴D method is employed for monitoring the passage of AMX and CTZ from the blood circulatory system into the subcutaneous tissue at the sites of diabetic ulceration in patients suffering from diabetic foot syndrome and also for measuring the pharmacokinetics following intravenous application of bolus antibiotic doses.     

Covalent anionic copolymer coatings with tunable electroosmotic flow for optimization of capillary electrophoretic separations

We present a method for finely adjustable electroosmotic flow (EOF) velocity in cathodic direction for the optimization of separations in capillary electrophoresis. To this end, we use surface modification of the separation fused silica capillary by the covalently attached copolymer of acrylamide (AM) and 2-acrylamido-2-methyl-1-propanesulfonate (AMPS), that is, poly(AM-co-AMPS) or PAMAMPS. Coatings were formed by the in-capillary polymerization of a mixture of the neutral AM and anionic AMPS monomers premixed in various ratios in order to control the charge density of the copolymer. EOF mobility varies in the 0 to ∼40 × 10⁻⁹ m² V⁻¹ s⁻¹ interval for PAMAMPS coatings ranging from 0 to 60 mol.% of charged AMPS monomer. For EOF in PAMAMPS-treated capillaries, we observed (i) a negligible dependence on pH in the 2–10 interval, (ii) a minor variance among background electrolytes (BGEs) in function of their components and (iii) its standard decrease with increasing ionic strength of the BGE. Interest in variable cathodic EOF was demonstrated by the amelioration of separation of two kinds of isomeric anionic analytes, that is, monosaccharides phosphates and helquat enantiomers, in counter-EOF mode.     

Fingerprinting pre-historical symbolic artefacts by a non-destructive methodological approach

Journal of Radioanalytical and Nuclear Chemistry - A contribution to the discussion about Vila Nova de São Pedro (VNSP) as a production centre of symbolic lithic artefacts, the origin of raw...     

Challenges for impedimetric affinity sensors targeting protein detection

The review provides articles discussing big challenges behind successful design of impedimetric biosensors and the way such challenges were/could be addressed for highly sensitive affinity detection of proteins. In particular, the effect of gold etching by chloride ions or by CN^? ions (released from the redox probe [Fe(CN)₆]^3-/4-), the effect of ionic strength of the assay buffer; the effect of initial interfacial properties (capacitance) and the effect of the high analyte:bioreceptor ratio on electrochemical impedance spectroscopy–based biosensing are discussed. The review provides also short discussion related to other factors, which can significantly affect operational performance of electrochemical impedance spectroscopy–based biosensing including novel conductive interfaces, small bioreceptors, strategies for improved selectivity (nonbiofouling interfaces) and sensitivity (use of nanoparticles).     

Theranostic Approach for the Protein Corona of Polysaccharide Nanoparticles

Polysaccharide nanoparticles are promising materials in the wide range of disciplines such as medicine, nutrition, food production, agriculture, material science and others. They excel not only in their non‐toxicity and biodegradability but also in their easy preparation. As well as inorganic particles, a protein corona (PC) around polysaccharide nanoparticles is formed in biofluids. Moreover, it has been considered that the overall response of the organism to nanoparticles presence depends on the PC. This review summarises scientific publications about the structural chemistry of polysaccharide nanoparticles and their impact on theranostic applications. Three strategies of implementation of the PC in theranostics have been discussed: I) Utilisation of the PC in therapy; II) How the composition of the PC is analysed for specific disease markers; III) How the formed PC can interact with the immune system and enhances the immunomodulation or immunoelimination. Thus, the findings from this review can contribute to improve the design of drug delivery systems. However, it is still necessary to elucidate the mechanisms of nano‐bio interactions and discover new connections in nanoscale research.     

Cyanines comprising barbiturate group facilitate NIR-light assisted ATRP under anaerobic and aerobic conditions at two wavelengths using Fe(III) catalyst

Cyanines with heptamethine pattern namely 5-(6-(2-(3-ethyl-1,1-dimethyl-1H-benzo[e]indol-2(3H)-ylidene)ethylidene)-2-(2-(3-ethyl-1,1-dimethyl-1H-benzo[e]indol-3-ium-2yl) vinyl) cyclo-hex-1-en-1-yl)-1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydropyrimidin-4-olate comprising a barbiturate group facilitate controlled radical polymerization using FeBr₃ in the ppm range applying radiation at 790 nm. Tris(4-methoylphenyl)phosphine, Tris(2-pyridylmethyl)amine or tetrabutylammonium bromide served as ligand. The latter showed the best performance resulting in a system needing no amino nitrogen for photo-ATRP. Ethyl α-bromophenylacetate worked as initiator. The cyanine interacts with FeBr₃ resulting in a new absorption band at 877 nm that also resulted in formation of polymer exhibiting similar molecular weight but higher dispersity compared to that obtained by 790 nm radiation by exposure with a light-emitting diode (LED) emitting at 870 nm. This explains the reactivity of the system while other cyanines such as 2-[2-[3-[2-(1,3-Dihydro-1,3,3-trimethyl-2H-indol-2-ylidene)-ethylidene]-2-(1-phenyl- 1H-tetrazol-5-ylsulfanyl)-1-cyclohexen-1-yl]-ethenyl]-1,3,3-trimethyl-3H-indolium chloride showed no activity by exposure at 790 nm in combination with FeBr₃/Br⁻. Controlled radical polymerization was confirmed by successful chain extension and block copolymerization experiments resulting in polymers, which exhibit a dispersity of about 1.3. Interestingly, the new system comprising the aforementioned barbiturate substituted cyanine, FeBr₃/Br⁻ and ethyl α-bromophenylacetate showed a certain oxygen tolerance. Polymers obtained exhibited similar dispersity as those made under inert conditions.