New reactivity of the uranyl ion: ring opening polymerisation of epoxides

The uranyl aryloxide, [UO(2)(OAr)(2)(THF)(2)], and uranyl chloride, [UO(2)Cl(2)(THF)(3)] or [UO(2)Cl(2)(THF)(2)](2) act as pre-catalysts for the ring opening polymerization of propylene oxide and cyclohexene oxide. Coordination of the monomers has been investigated using (1)H EXSY spectroscopy and kinetic and thermodynamic parameters reported. NMR analyses of the polymers suggest a bimetallic mechanism for the polymerization.     

Procaine effect on human erythrocyte membrane explored by atomic force microscopy

The procaine effect on human erythrocytes was investigated by atomic force microscopy (AFM) at three procaine concentrations, about 5 x 10(-7) M, 5 x 10(-5) M and 5 x 10(-4) M. The changes in surface morphology of erythrocyte membrane bring direct evidence on the procaine effect on the cell membrane at micro- and nanometer scale. AFM images of the control erythrocytes (without procaine) showed a well defined concave (donut) shape of cells. The structure of control erythrocytes membrane is featured by closely packed nanometer size intra-membranous particles. After the incubation of the fresh blood with increasing procaine concentrations, a progressive increase in both concave depth and surface roughness of erythrocyte membrane was observed. The particles (granules) of the membrane surface increased progressively with increasing procaine concentrations. The changes in the surface morphology of erythrocyte membrane can be associated with the enlargement of surface granules, due to the aggregation of membranous particles within the cell surface, and the domain structure formation induced by procaine. A large number of moderate elevations from 25 nm to almost 40 nm in lateral size were found to be rather uniformly distributed on the surface of whole erythrocytes at low and medium procaine concentrations, respectively. At the highest procaine concentration, the granules of about 80 nm to almost 90 nm lateral size were found to form rows rather well separated. These data are in substantial agreement with the published results obtained on membrane models in the presence of procaine.     

Indirect cathodic reduction of dispersed indigo by 1,2-dihydroxy-9,10-anthraquinone-3-sulphonate (Alizarin Red S)

The indirect cathodic reduction of dispersed indigo (Vat Blue 1) with 1,2-dihydroxy-9,10-anthraquinone-3-sulphonate (Alizarin Red S) as soluble mediator system was studied in 0.1 M NaOH by cyclic voltammetry, voltammetry in a flow cell and in galvanostatic reduction experiments. In cyclic voltammetry, the presence of 17.1 mM indigo led to an increase in the diffusion-controlled cathodic peak current (I _p)_d by a factor of 2. During the reverse scan of the voltammograms the oxidation of reduced indigo could be observed at −650 mV (vs. Ag/AgCl, 3 M KCl). In voltrammograms of 4.0 mM ALS in 0.1 M NaOH, recorded in a flow cell, a current density of 0.40–0.46 mA cm⁻² was determined for the diffusion-controlled cathodic current plateau, which appeared in the potential range of −850 to −1,050 mV. In galvanostatic batch electrolysis, solutions containing 2.5–3.8 mM reduced indigo were prepared and analysed by spectrophotometry and tested in dyeing experiments. The dyeing behaviour of the reduced indigo was independent of the reduction technique used. Energy consumption for electrochemical reduction of 1 kg of indigo could be estimated to 6.5 kWh kg⁻¹.     

Suitability of ionic liquids as mobile‐phase additives in HPLC with fluorescence and UV detection for the determination of heterocyclic aromatic amines

The effects of several ionic liquids (ILs) as mobile‐phase additives in HPLC with fluorescence and UV–Vis detection for the determination of six heterocyclic aromatic amines were evaluated using two different C₁₈ stationary phases with moderate silanol activity. The studied ILs were 1‐butyl‐3‐methylimidazolium tetrafluoroborate, 1‐hexyl‐3‐methylimidazolium tetrafluoroborate and 1‐methyl‐3‐octylimidazolium tetrafluoroborate. The optical behaviour of heterocyclic aromatic amines in presence of ILs was studied and the silanol‐suppressing potency of ILs was evaluated for the two stationary phases studied. Several chromatographic parameters were evaluated in the presence or absence of ILs, or using triethylamine, the most common mobile‐phase additive. The best results were achieved using 1 mM 1‐butyl‐3‐methylimidazolium tetrafluoroborate as mobile‐phase additive and NovaPak^® column. In these conditions and with 18% of ACN in the mobile phase, analytical performance of the chromatographic methods using fluorescence and UV–Vis were evaluated, obtaining good precision in all cases (RSD lower than 6.6%) and low LOD (0.001–0.147 μg/mL with UV–Vis and 0.001–0.006 ng/mL with fluorescence detection).     

Advances in thermoanalytical techniques

Journal of Thermal Analysis and Calorimetry - Thermogravimetry coupled with chemometrics has proved to be a rapid and cost-effective diagnostic tool for β-thalassemia screening. This model,...     

ChemNetworks: A complex network analysis tool for chemical systems

Many intermolecular chemical interactions persist across length and timescales and can be considered to form a “network” or “graph.” Obvious examples include the hydrogen bond networks formed by polar solvents such as water or alcohols. In fact, there are many similarities between intermolecular chemical networks like those formed by hydrogen bonding and the complex and distributed networks found in computer science. Contemporary network analyses are able to dissect the complex local and global changes that occur within the network over multiple time and length scales. This work discusses the ChemNetworks software, whose purpose is to process Cartesian coordinates of chemical systems into a network/graph formalism and apply topological network analyses that include network neighborhood, the determination of geodesic paths, the degree census, direct structural searches, and the distribution of defect states of network. These properties can help to understand the network patterns and organization that may influence physical properties and chemical reactivity. The focus of ChemNetworks is to quantitatively describe intermolecular chemical networks of entire systems at both the local and global levels and as a function of time. The code is highly general, capable of converting a wide variety of systems into a chemical network formalism, including complex solutions, liquid interfaces, or even self‐assemblies. © 2013 Wiley Periodicals, Inc.     

Effect of Laser Thermal Injury on Langerhans Cells in Mouse and Hairless Guinea Pig Epidermis

To examine the effect of laser thermal injury on Langerhans cells (LC) within the epidermis, the dorsal skin of mice and hairless guinea pigs was exposed to varying levels of laser irradiation using a thulium laser at a wavelength of 2.0 μm. At 6, 24 and 48 h post irradiation, animals were euthanized, skin samples prepared for histology and the epidermis obtained and stained by major histocompatibility complex‐II staining (mice) or ATPase assay (hairless guinea pigs) for the enumeration of LC. Mouse skin exhibited histological evidence of thermal damage at 24 h post irradiation at even the lowest dose (0.14 W) and decreases in the numbers of epidermal LC were observed at all doses and decreases were proportional to dose. In contrast, hairless guinea pig skin only showed consistent histological evidence of thermal damage at the highest dose of irradiation (0.70 W) at 24 and 48 h post irradiation and exhibited a statistically significant decrease in numbers of epidermal LC only at this dose. Thus, epidermal LC depletion occurred in the skin of both mice and hairless guinea pigs in response to laser treatment and the magnitude of depletion directly correlated with the extent of thermal damage both within and between species.